485BPOS

As filed with the U.S. Securities and Exchange Commission on August 7, 2018

Securities Act File No. 333-224376

Investment Company Act File No. 811-23346

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933	☒
Pre-Effective Amendment No.	☐
Post-Effective Amendment No. 1	☒

and/or

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940	☒
Amendment No. 2

(Check appropriate box or boxes)

BlackRock Variable Series Funds II, Inc.

(Exact Name of Registrant as Specified in Charter)

100 Bellevue Parkway

Wilmington, Delaware 19809

(Address of Principal Executive Office)

Registrant’s Telephone Number, including Area Code (800) 441-7762

John M. Perlowski

BlackRock Variable Series Funds II, Inc.

55 East 52^nd Street, New York, New York 10055

(Name and Address of Agent for Service)

Copies to:

Counsel for the Fund:
Margery K. Neale, Esq.
Willkie Farr & Gallagher LLP
787 Seventh Avenue
New York, New York 10019-6099 Benjamin Archibald, Esq.
BlackRock Advisors, LLC
55 East 52^nd Street
New York, New York 10055

Continuous

(Approximate Date of Proposed Offering)

It is proposed that this filing will become effective:

☒ immediately upon filing pursuant to paragraph (b)

☐ on (date) pursuant to paragraph (b)

☐ 60 days after filing pursuant to paragraph (a)(1)

☐ on (date) pursuant to paragraph (a)(1)

☐ 75 days after filing pursuant to paragraph (a)(2)

☐ on (date) pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:

☐ This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

Title of Securities Being Registered: Shares of Common Stock, par value, $0.0001 per share.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all the requirements for the effectiveness of this Post-Effective Amendment to its Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this Post-Effective Amendment to its Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of New York and the State of New York, on August 7, 2018.

BLACKROCK VARIABLE SERIES FUNDS II, INC.
(Registrant)
By:	/s/ JOHN M. PERLOWSKI
	(John M. Perlowski,
	President and Chief Executive Officer)
	(Principal Executive Officer)

Pursuant to the requirements of the Securities Act of 1933, this Post-Effective Amendment to its Registration Statement has been signed below by the following persons in the capacities and on the dates indicated:

Signature	Title	Date
/S/ JOHN M. PERLOWSKI John M. Perlowski	Director, President and Chief Executive Officer (Principal Executive Officer)	August 7, 2018
/S/ NEAL J. ANDREWS Neal J. Andrews	Chief Financial Officer (Principal Financial and Accounting Officer)	August 7, 2018
JAMES H. BODURTHA* (James H. Bodurtha)	Director
BRUCE R. BOND* (Bruce R. Bond)	Director
STUART E. EIZENSTAT* (Stuart E. Eizenstat)	Director
HENRY GABBAY* (Henry Gabbay)	Director
LENA G. GOLDBERG* (Lena G. Goldberg)	Director
ROBERT M. HERNANDEZ* (Robert M. Hernandez)	Director
HENRY R. KEIZER* (Henry R. Keizer)	Director
JOHN F. O’BRIEN* (John F. O’Brien)	Director

- 3 -

DONALD C. OPATRNY* (Donald C. Opatrny)	Director
ROBERT FAIRBAIRN* (Robert Fairbairn)	Director

*By:	/S/ BENJAMIN ARCHIBALD	August 7, 2018
	Benjamin Archibald (Attorney-in-Fact)

- 4 -

EXHIBIT INDEX

Index No.	Description of Exhibit
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase

- 5 -

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Dec. 31, 2017
Registrant Name	dei_EntityRegistrantName	BlackRock Variable Series Funds II, Inc.
Central Index Key	dei_EntityCentralIndexKey	0001738072
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Jul. 02, 2018
Document Effective Date	dei_DocumentEffectiveDate	Jul. 17, 2018
Prospectus Date	rr_ProspectusDate	Jul. 02, 2018

XML

BlackRock High Yield V.I. Fund

Fund Overview

Key Facts About BlackRock High Yield V.I. Fund

Investment Objective

The investment objective of the BlackRock High Yield V.I. Fund (the “Fund”) is to seek to maximize total return, consistent with income generation and prudent investment management.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. The expenses below do not include separate account fees and expenses, and would be higher if these fees and expenses were included. Please refer to your variable annuity or insurance contract (the “Contract”) prospectus for information on the separate account fees and expenses associated with your Contract.

Shareholder Fees (fees paid directly from your investment)

The Fund is not subject to any shareholder fees.

Annual Fund Operating Expenses
(expenses that you pay each year as a
percentage of the value of your investment)

Annual Fund Operating Expenses - BlackRock High Yield V.I. Fund		Class I Shares	Class III Shares
Management Fees	[1],[2]	0.50%	0.50%
Distribution and/or Service (12b-1) Fees		none	0.25%
Other Expenses	[3]	0.28%	0.28%
Acquired Fund Fees and Expenses	[3],[4]	0.01%	0.01%
Total Annual Fund Operating Expenses	[4]	0.79%	1.04%
Fee Waivers and/or Expense Reimbursements	[1],[5]	(0.10%)	(0.11%)
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	[1],[5]	0.69%	0.93%

Example:

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The Example does not reflect charges imposed by the Contract. See the Contract prospectus for information on such charges. Although your actual costs may be higher or lower, based on these assumptions and the net expenses shown in the fee table, your costs would be:

Expense Example - BlackRock High Yield V.I. Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Class I Shares	70	242	429	969
Class III Shares	95	320	563	1,261

Portfolio Turnover:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance.

The Fund has not commenced operations as of the date of this prospectus, but it is expected that BlackRock High Yield V.I. Fund, a series of BlackRock Variable Series Funds, Inc. (the “Predecessor Fund”), will be reorganized into the Fund. During the most recent fiscal year, the Predecessor Fund’s portfolio turnover rate was 75% of the average value of its portfolio.

Principal Investment Strategies of the Fund

The Fund invests primarily in non-investment grade bonds with maturities of ten years or less. The Fund normally invests at least 80% of its assets in high yield bonds. The Fund may also invest in convertible and preferred securities. These securities will be counted toward the Fund’s 80% policy to the extent they have characteristics similar to the securities included within that policy. The high yield securities (commonly called “junk bonds”) acquired by the Fund will generally be in the lower rating categories of the major rating agencies (BB or lower by Standard & Poor’s (“S&P”) or Fitch Ratings, Inc. (“Fitch”), or Ba or lower by Moody’s Investor Services (“Moody’s”)) or will be determined by the Fund management team to be of similar quality. Split rated bonds will be considered to have the higher credit rating. The Fund may invest up to 30% of its assets in non-dollar denominated bonds of issuers located outside of the United States. The Fund’s investment in non-dollar denominated bonds may be on a currency hedged or unhedged basis.

To add additional diversification, the management team can invest in a wide range of securities including corporate bonds, mezzanine investments, collateralized bond obligations, bank loans and mortgage-backed and asset-backed securities. The Fund can also invest, to the extent consistent with its investment objective, in non-U.S. and emerging market securities and currencies. The Fund may invest in securities of any rating, and may invest up to 10% of its assets (measured at the time of investment) in distressed securities that are in default or the issuers of which are in bankruptcy.

The Fund may buy or sell options or futures on a security or an index of securities, or enter into credit default swaps and interest rate or foreign currency transactions, including swaps (collectively, commonly known as derivatives). The Fund may use derivative instruments to hedge its investments or to seek to enhance returns. The Fund may seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as reverse repurchase agreements or dollar rolls).

The Fund may engage in active and frequent trading of portfolio securities to achieve its principal investment strategies.

Principal Risks of Investing in the Fund

Risk is inherent in all investing. The value of your investment in the Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund.

• Bank Loan Risk — The market for bank loans may not be highly liquid and the Fund may have difficulty selling them. These investments expose the Fund to the credit risk of both the financial institution and the underlying borrower.

• Collateralized Bond Obligation Risk — The pool of high yield securities underlying collateralized bond obligations is typically separated into groupings called tranches representing different degrees of credit quality. The higher quality tranches have greater degrees of protection and pay lower interest rates. The lower tranches, with greater risk, pay higher interest rates.

• Convertible Securities Risk — The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest or dividends when due, and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock.

• Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.
  
  Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise. The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management. To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities. These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change. A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
  
  Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.
  
  Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
  
  Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.

• Derivatives Risk — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:
  
  Volatility Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.
  
  Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation.
  
  Market and Liquidity Risk — The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately.
  
  Valuation Risk — Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them.
  
  Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences.
  
  Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments.
  
  Regulatory Risk — Derivative contracts, including, without limitation, swaps, currency forwards and non-deliverable forwards, are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (“Dodd-Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, certain derivatives are subject to margin requirements and swap dealers are required to collect margin from the Fund with respect to such derivatives. Specifically, regulations are now in effect that require swap dealers to post and collect variation margin (comprised of specified liquid instruments and subject to a required haircut) in connection with trading of over-the-counter (“OTC”) swaps with the Fund. Shares of investment companies (other than certain money market funds) may not be posted as collateral under these regulations. Requirements for posting of initial margin in connection with OTC swaps will be phased-in through 2020. In addition, regulations adopted by prudential regulators that will begin to take effect in 2019 will require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Fund, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Fund of trading in these instruments and, as a result, may affect returns to investors in the Fund.

• Distressed Securities Risk — Distressed securities are speculative and involve substantial risks in addition to the risks of investing in junk bonds. The Fund will generally not receive interest payments on the distressed securities and may incur costs to protect its investment. In addition, distressed securities involve the substantial risk that principal will not be repaid. These securities may present a substantial risk of default or may be in default at the time of investment. The Fund may incur additional expenses to the extent it is required to seek recovery upon a default in the payment of principal of or interest on its portfolio holdings. In any reorganization or liquidation proceeding relating to a portfolio company, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Distressed securities and any securities received in an exchange for such securities may be subject to restrictions on resale.

• Dollar Rolls Risk — Dollar rolls involve the risk that the market value of the securities that the Fund is committed to buy may decline below the price of the securities the Fund has sold. These transactions may involve leverage.

• Emerging Markets Risk — Emerging markets are riskier than more developed markets because they tend to develop unevenly and may never fully develop. Investments in emerging markets may be considered speculative. Emerging markets are more likely to experience hyperinflation and currency devaluations, which adversely affect returns to U.S. investors. In addition, many emerging securities markets have far lower trading volumes and less liquidity than developed markets.

• Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include:

• The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight.

• Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio.

• The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position.

• The governments of certain countries may prohibit or impose substantial restrictions on foreign investments in their capital markets or in certain industries.

• Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws.

• Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments.

• The European financial markets have recently experienced volatility and adverse trends due to concerns about economic downturns in, or rising government debt levels of, several European countries. These events may spread to other countries in Europe. These events may affect the value and liquidity of certain of the Fund’s investments.

• High Portfolio Turnover Risk — The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of Fund portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect Fund performance.

• Junk Bonds Risk — Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that are considered speculative and may cause income and principal losses for the Fund.

• Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.

• Liquidity Risk — Liquidity risk exists when particular investments are difficult to purchase or sell. The Fund’s investments in illiquid securities may reduce the returns of the Fund because it may be difficult to sell the illiquid securities at an advantageous time or price. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to liquidity risk. Liquidity risk may be the result of, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active market. Liquid investments may become illiquid or less liquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid and relatively less liquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. This may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed-income mutual funds may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions.

• Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.

• Mezzanine Securities Risk — Mezzanine securities carry the risk that the issuer will not be able to meet its obligations and that the equity securities purchased with the mezzanine investments may lose value.

• Mortgage- and Asset-Backed Securities Risks — Mortgage- and asset-backed securities represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. Mortgage- and asset-backed securities are subject to credit, interest rate, prepayment and extension risks. These securities also are subject to risk of default on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities.

• Preferred Securities Risk — Preferred securities may pay fixed or adjustable rates of return. Preferred securities are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred securities generally pay dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred securities will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. Preferred securities of smaller companies may be more vulnerable to adverse developments than preferred stock of larger companies.

• Repurchase Agreements and Purchase and Sale Contracts Risk — If the other party to a repurchase agreement or purchase and sale contract defaults on its obligation under the agreement, the Fund may suffer delays and incur costs or lose money in exercising its rights under the agreement. If the seller fails to repurchase the security in either situation and the market value of the security declines, the Fund may lose money.

• Reverse Repurchase Agreements Risk — Reverse repurchase agreements involve the sale of securities held by the Fund with an agreement to repurchase the securities at an agreed-upon price, date and interest payment. Reverse repurchase agreements involve the risk that the other party may fail to return the securities in a timely manner or at all. The Fund could lose money if it is unable to recover the securities and the value of the collateral held by the Fund, including the value of the investments made with cash collateral, is less than the value of the securities. These events could also trigger adverse tax consequences to the Fund.

Performance Information

The Fund has not commenced operations as of the date of this prospectus. The returns presented for the Fund reflect the performance of the Predecessor Fund. It is anticipated that on or about September 17, 2018, the Fund will acquire all of the assets, subject to the liabilities, of the Predecessor Fund through a tax-free reorganization (the “Reorganization”). As a result of the Reorganization, the Fund will adopt the performance and financial history of the Predecessor Fund. The Reorganization is being consummated in connection with a potential reconfiguration of the existing fund complexes overseen by the boards of directors/trustees of the BlackRock-advised funds. The Fund has the same investment objectives, strategies and policies, portfolio management team and contractual arrangements, including the same contractual fees and expenses, as the Predecessor Fund. As a result, the performance of the Fund would have been substantially similar to that of the Predecessor Fund.

The information shows you how the Predecessor Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The Predecessor Fund’s returns prior to October 1, 2011 as reflected in the bar chart and the table are the returns of the Predecessor Fund that followed different investment objectives and investment strategies under the name “BlackRock High Income V.I. Fund.” The table compares the Predecessor Fund’s performance to that of the Bloomberg Barclays U.S. Corporate High Yield 2% Issuer Capped Index. As with all such investments, past performance is not an indication of future results. The bar chart and table do not reflect separate account fees and expenses. If they did, returns would be less than those shown. The returns for Class III Shares prior to February 15, 2012, the recommencement of operations of Class III Shares, are based upon performance of the Predecessor Fund’s Class I Shares, as adjusted to reflect the distribution and/or service (12b-1) fees applicable to Class III Shares. This information may be considered when assessing the performance of Class III Shares, but does not represent the actual performance of Class III Shares. To the extent that dividends and distributions have been paid by the Predecessor Fund, the performance information for the Predecessor Fund in the chart and table assumes reinvestment of the dividends and distributions. If the Predecessor Fund’s investment manager and its affiliates had not waived or reimbursed certain Predecessor Fund expenses during these periods, the Predecessor Fund’s returns would have been lower.

Class I Shares
ANNUAL TOTAL RETURNS
BlackRock High Yield V.I. Fund
As of 12/31

During the ten-year period shown in the bar chart, the highest return for a quarter was 19.69% (quarter ended June 30, 2009) and the lowest return for a quarter was -23.39% (quarter ended December 31, 2008).

As of 12/31/17
Average Annual Total Returns

Average Annual Total Returns - BlackRock High Yield V.I. Fund	1 Year	5 Years	10 Years
Class I Shares	7.48%	5.65%	7.23%
Class III Shares	7.08%	5.37%	6.95%
Bloomberg Barclays U.S. Corporate High Yield 2% Issuer Capped Index (Reflects no deduction for fees, expenses or taxes)	7.50%	5.78%	8.09%

[1] As described in the “Management of the Funds” section of the Fund’s prospectus, BlackRock Advisors, LLC (“BlackRock”) has contractually agreed to waive the management fee with respect to any portion of the Fund’s assets estimated to be attributable to investments in other equity and fixed-income mutual funds and exchange-traded funds managed by BlackRock or its affiliates that have a contractual management fee, through April 30, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of BlackRock Variable Series Funds II, Inc. (the “Company”) or by a vote of a majority of the outstanding voting securities of the Fund.

[2] Management Fee is based on the management fee rate of the Predecessor Fund (defined below).

[3] Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year, which are based on the expenses of the Predecessor Fund for its most recent fiscal year.

[4] The Total Annual Fund Operating Expenses do not correlate to the ratio of expenses to average net assets given in the Predecessor Fund’s most recent annual report, which does not include Acquired Fund Fees and Expenses.

[5] As described in the “Management of the Funds” section of the Fund’s prospectus, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 1.25% (for Class I Shares) and 1.50% (for Class III Shares) of average daily net assets through April 30, 2020. BlackRock has also contractually agreed to reimburse fees in order to limit certain operational and recordkeeping fees to 0.06% (for Class I Shares) and 0.05% (for Class III Shares) of average daily net assets through April 30, 2020. Each of these contractual agreements may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Company or by a vote of a majority of the outstanding voting securities of the Fund.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	BlackRock Variable Series Funds II, Inc.
Prospectus Date	rr_ProspectusDate	Jul. 02, 2018
BlackRock High Yield V.I. Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Overview Key Facts About BlackRock High Yield V.I. Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the BlackRock High Yield V.I. Fund (the “Fund”) is to seek to maximize total return, consistent with income generation and prudent investment management.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses of the Fund
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. The expenses below do not include separate account fees and expenses, and would be higher if these fees and expenses were included. Please refer to your variable annuity or insurance contract (the “Contract”) prospectus for information on the separate account fees and expenses associated with your Contract.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment) The Fund is not subject to any shareholder fees.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	April 30, 2020
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. The Fund has not commenced operations as of the date of this prospectus, but it is expected that BlackRock High Yield V.I. Fund, a series of BlackRock Variable Series Funds, Inc. (the “Predecessor Fund”), will be reorganized into the Fund. During the most recent fiscal year, the Predecessor Fund’s portfolio turnover rate was 75% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	75.00%
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year, which are based on the expenses of the Predecessor Fund for its most recent fiscal year.
Acquired Fund Fees and Expenses, Based on Estimates [Text]	rr_AcquiredFundFeesAndExpensesBasedOnEstimates	Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year, which are based on the expenses of the Predecessor Fund for its most recent fiscal year.
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	The Total Annual Fund Operating Expenses do not correlate to the ratio of expenses to average net assets given in the Predecessor Fund’s most recent annual report, which does not include Acquired Fund Fees and Expenses.
Expense Example [Heading]	rr_ExpenseExampleHeading	Example:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The Example does not reflect charges imposed by the Contract. See the Contract prospectus for information on such charges. Although your actual costs may be higher or lower, based on these assumptions and the net expenses shown in the fee table, your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies of the Fund
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund invests primarily in non-investment grade bonds with maturities of ten years or less. The Fund normally invests at least 80% of its assets in high yield bonds. The Fund may also invest in convertible and preferred securities. These securities will be counted toward the Fund’s 80% policy to the extent they have characteristics similar to the securities included within that policy. The high yield securities (commonly called “junk bonds”) acquired by the Fund will generally be in the lower rating categories of the major rating agencies (BB or lower by Standard & Poor’s (“S&P”) or Fitch Ratings, Inc. (“Fitch”), or Ba or lower by Moody’s Investor Services (“Moody’s”)) or will be determined by the Fund management team to be of similar quality. Split rated bonds will be considered to have the higher credit rating. The Fund may invest up to 30% of its assets in non-dollar denominated bonds of issuers located outside of the United States. The Fund’s investment in non-dollar denominated bonds may be on a currency hedged or unhedged basis. To add additional diversification, the management team can invest in a wide range of securities including corporate bonds, mezzanine investments, collateralized bond obligations, bank loans and mortgage-backed and asset-backed securities. The Fund can also invest, to the extent consistent with its investment objective, in non-U.S. and emerging market securities and currencies. The Fund may invest in securities of any rating, and may invest up to 10% of its assets (measured at the time of investment) in distressed securities that are in default or the issuers of which are in bankruptcy. The Fund may buy or sell options or futures on a security or an index of securities, or enter into credit default swaps and interest rate or foreign currency transactions, including swaps (collectively, commonly known as derivatives). The Fund may use derivative instruments to hedge its investments or to seek to enhance returns. The Fund may seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as reverse repurchase agreements or dollar rolls). The Fund may engage in active and frequent trading of portfolio securities to achieve its principal investment strategies.
Risk [Heading]	rr_RiskHeading	Principal Risks of Investing in the Fund
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Risk is inherent in all investing. The value of your investment in the Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund. Bank Loan Risk — The market for bank loans may not be highly liquid and the Fund may have difficulty selling them. These investments expose the Fund to the credit risk of both the financial institution and the underlying borrower. Collateralized Bond Obligation Risk — The pool of high yield securities underlying collateralized bond obligations is typically separated into groupings called tranches representing different degrees of credit quality. The higher quality tranches have greater degrees of protection and pay lower interest rates. The lower tranches, with greater risk, pay higher interest rates. Convertible Securities Risk — The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest or dividends when due, and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock. Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things. Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise. The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management. To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities. These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change. A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance. Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation. Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall. Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields. Derivatives Risk — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including: Volatility Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets. Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation. Market and Liquidity Risk — The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately. Valuation Risk — Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them. Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences. Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments. Regulatory Risk — Derivative contracts, including, without limitation, swaps, currency forwards and non-deliverable forwards, are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (“Dodd-Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, certain derivatives are subject to margin requirements and swap dealers are required to collect margin from the Fund with respect to such derivatives. Specifically, regulations are now in effect that require swap dealers to post and collect variation margin (comprised of specified liquid instruments and subject to a required haircut) in connection with trading of over-the-counter (“OTC”) swaps with the Fund. Shares of investment companies (other than certain money market funds) may not be posted as collateral under these regulations. Requirements for posting of initial margin in connection with OTC swaps will be phased-in through 2020. In addition, regulations adopted by prudential regulators that will begin to take effect in 2019 will require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Fund, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Fund of trading in these instruments and, as a result, may affect returns to investors in the Fund. Distressed Securities Risk — Distressed securities are speculative and involve substantial risks in addition to the risks of investing in junk bonds. The Fund will generally not receive interest payments on the distressed securities and may incur costs to protect its investment. In addition, distressed securities involve the substantial risk that principal will not be repaid. These securities may present a substantial risk of default or may be in default at the time of investment. The Fund may incur additional expenses to the extent it is required to seek recovery upon a default in the payment of principal of or interest on its portfolio holdings. In any reorganization or liquidation proceeding relating to a portfolio company, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Distressed securities and any securities received in an exchange for such securities may be subject to restrictions on resale. Dollar Rolls Risk — Dollar rolls involve the risk that the market value of the securities that the Fund is committed to buy may decline below the price of the securities the Fund has sold. These transactions may involve leverage. Emerging Markets Risk — Emerging markets are riskier than more developed markets because they tend to develop unevenly and may never fully develop. Investments in emerging markets may be considered speculative. Emerging markets are more likely to experience hyperinflation and currency devaluations, which adversely affect returns to U.S. investors. In addition, many emerging securities markets have far lower trading volumes and less liquidity than developed markets. Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include: The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight. Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio. The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position. The governments of certain countries may prohibit or impose substantial restrictions on foreign investments in their capital markets or in certain industries. Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws. Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments. The European financial markets have recently experienced volatility and adverse trends due to concerns about economic downturns in, or rising government debt levels of, several European countries. These events may spread to other countries in Europe. These events may affect the value and liquidity of certain of the Fund’s investments. High Portfolio Turnover Risk — The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of Fund portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect Fund performance. Junk Bonds Risk — Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that are considered speculative and may cause income and principal losses for the Fund. Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage. Liquidity Risk — Liquidity risk exists when particular investments are difficult to purchase or sell. The Fund’s investments in illiquid securities may reduce the returns of the Fund because it may be difficult to sell the illiquid securities at an advantageous time or price. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to liquidity risk. Liquidity risk may be the result of, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active market. Liquid investments may become illiquid or less liquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid and relatively less liquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. This may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed-income mutual funds may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions. Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money. Mezzanine Securities Risk — Mezzanine securities carry the risk that the issuer will not be able to meet its obligations and that the equity securities purchased with the mezzanine investments may lose value. Mortgage- and Asset-Backed Securities Risks — Mortgage- and asset-backed securities represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. Mortgage- and asset-backed securities are subject to credit, interest rate, prepayment and extension risks. These securities also are subject to risk of default on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities. Preferred Securities Risk — Preferred securities may pay fixed or adjustable rates of return. Preferred securities are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred securities generally pay dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred securities will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. Preferred securities of smaller companies may be more vulnerable to adverse developments than preferred stock of larger companies. Repurchase Agreements and Purchase and Sale Contracts Risk — If the other party to a repurchase agreement or purchase and sale contract defaults on its obligation under the agreement, the Fund may suffer delays and incur costs or lose money in exercising its rights under the agreement. If the seller fails to repurchase the security in either situation and the market value of the security declines, the Fund may lose money. Reverse Repurchase Agreements Risk — Reverse repurchase agreements involve the sale of securities held by the Fund with an agreement to repurchase the securities at an agreed-upon price, date and interest payment. Reverse repurchase agreements involve the risk that the other party may fail to return the securities in a timely manner or at all. The Fund could lose money if it is unable to recover the securities and the value of the collateral held by the Fund, including the value of the investments made with cash collateral, is less than the value of the securities. These events could also trigger adverse tax consequences to the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not commenced operations as of the date of this prospectus. The returns presented for the Fund reflect the performance of the Predecessor Fund. It is anticipated that on or about September 17, 2018, the Fund will acquire all of the assets, subject to the liabilities, of the Predecessor Fund through a tax-free reorganization (the “Reorganization”). As a result of the Reorganization, the Fund will adopt the performance and financial history of the Predecessor Fund. The Reorganization is being consummated in connection with a potential reconfiguration of the existing fund complexes overseen by the boards of directors/trustees of the BlackRock-advised funds. The Fund has the same investment objectives, strategies and policies, portfolio management team and contractual arrangements, including the same contractual fees and expenses, as the Predecessor Fund. As a result, the performance of the Fund would have been substantially similar to that of the Predecessor Fund. The information shows you how the Predecessor Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The Predecessor Fund’s returns prior to October 1, 2011 as reflected in the bar chart and the table are the returns of the Predecessor Fund that followed different investment objectives and investment strategies under the name “BlackRock High Income V.I. Fund.” The table compares the Predecessor Fund’s performance to that of the Bloomberg Barclays U.S. Corporate High Yield 2% Issuer Capped Index. As with all such investments, past performance is not an indication of future results. The bar chart and table do not reflect separate account fees and expenses. If they did, returns would be less than those shown. The returns for Class III Shares prior to February 15, 2012, the recommencement of operations of Class III Shares, are based upon performance of the Predecessor Fund’s Class I Shares, as adjusted to reflect the distribution and/or service (12b-1) fees applicable to Class III Shares. This information may be considered when assessing the performance of Class III Shares, but does not represent the actual performance of Class III Shares. To the extent that dividends and distributions have been paid by the Predecessor Fund, the performance information for the Predecessor Fund in the chart and table assumes reinvestment of the dividends and distributions. If the Predecessor Fund’s investment manager and its affiliates had not waived or reimbursed certain Predecessor Fund expenses during these periods, the Predecessor Fund’s returns would have been lower.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The information shows you how the Predecessor Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund.
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	As with all such investments, past performance is not an indication of future results.
Bar Chart [Heading]	rr_BarChartHeading	Class I Shares ANNUAL TOTAL RETURNS BlackRock High Yield V.I. Fund As of 12/31
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The bar chart and table do not reflect separate account fees and expenses. If they did, returns would be less than those shown.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the ten-year period shown in the bar chart, the highest return for a quarter was 19.69% (quarter ended June 30, 2009) and the lowest return for a quarter was -23.39% (quarter ended December 31, 2008).
Performance Table Heading	rr_PerformanceTableHeading	As of 12/31/17 Average Annual Total Returns
BlackRock High Yield V.I. Fund | Class I Shares
Risk/Return:	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.50%	[1],[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.28%	[3]
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%	[3],[4]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.79%	[4]
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.10%)	[1],[5]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.69%	[1],[5]
1 Year	rr_ExpenseExampleYear01	$ 70
3 Years	rr_ExpenseExampleYear03	242
5 Years	rr_ExpenseExampleYear05	429
10 Years	rr_ExpenseExampleYear10	$ 969
2008	rr_AnnualReturn2008	(29.88%)
2009	rr_AnnualReturn2009	58.00%
2010	rr_AnnualReturn2010	15.34%
2011	rr_AnnualReturn2011	3.33%
2012	rr_AnnualReturn2012	15.65%
2013	rr_AnnualReturn2013	9.33%
2014	rr_AnnualReturn2014	2.89%
2015	rr_AnnualReturn2015	(3.60%)
2016	rr_AnnualReturn2016	12.92%
2017	rr_AnnualReturn2017	7.48%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	19.69%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(23.39%)
1 Year	rr_AverageAnnualReturnYear01	7.48%
5 Years	rr_AverageAnnualReturnYear05	5.65%
10 Years	rr_AverageAnnualReturnYear10	7.23%
BlackRock High Yield V.I. Fund | Class III Shares
Risk/Return:	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.50%	[1],[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.28%	[3]
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%	[3],[4]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.04%	[4]
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.11%)	[1],[5]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.93%	[1],[5]
1 Year	rr_ExpenseExampleYear01	$ 95
3 Years	rr_ExpenseExampleYear03	320
5 Years	rr_ExpenseExampleYear05	563
10 Years	rr_ExpenseExampleYear10	$ 1,261
1 Year	rr_AverageAnnualReturnYear01	7.08%
5 Years	rr_AverageAnnualReturnYear05	5.37%
10 Years	rr_AverageAnnualReturnYear10	6.95%
BlackRock High Yield V.I. Fund | Bloomberg Barclays U.S. Corporate High Yield 2% Issuer Capped Index (Reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	7.50%
5 Years	rr_AverageAnnualReturnYear05	5.78%
10 Years	rr_AverageAnnualReturnYear10	8.09%

[1] As described in the “Management of the Funds” section of the Fund’s prospectus, BlackRock Advisors, LLC (“BlackRock”) has contractually agreed to waive the management fee with respect to any portion of the Fund’s assets estimated to be attributable to investments in other equity and fixed-income mutual funds and exchange-traded funds managed by BlackRock or its affiliates that have a contractual management fee, through April 30, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of BlackRock Variable Series Funds II, Inc. (the “Company”) or by a vote of a majority of the outstanding voting securities of the Fund.

[2] Management Fee is based on the management fee rate of the Predecessor Fund (defined below).

[3] Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year, which are based on the expenses of the Predecessor Fund for its most recent fiscal year.

[4] The Total Annual Fund Operating Expenses do not correlate to the ratio of expenses to average net assets given in the Predecessor Fund’s most recent annual report, which does not include Acquired Fund Fees and Expenses.

[5] As described in the “Management of the Funds” section of the Fund’s prospectus, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 1.25% (for Class I Shares) and 1.50% (for Class III Shares) of average daily net assets through April 30, 2020. BlackRock has also contractually agreed to reimburse fees in order to limit certain operational and recordkeeping fees to 0.06% (for Class I Shares) and 0.05% (for Class III Shares) of average daily net assets through April 30, 2020. Each of these contractual agreements may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Company or by a vote of a majority of the outstanding voting securities of the Fund.

XML

BlackRock Total Return V.I. Fund

Fund Overview

Key Facts About BlackRock Total Return V.I. Fund

Investment Objective

The investment objective of the BlackRock Total Return V.I. Fund (the “Fund”) is to maximize total return, consistent with income generation and prudent investment management.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. The expenses below do not include separate account fees and expenses, and would be higher if these fees and expenses were included. Please refer to your variable annuity or insurance contract (the “Contract”) prospectus for information on the separate account fees and expenses associated with your Contract.

Shareholder Fees (fees paid directly from your investment)

The Fund is not subject to any shareholder fees.

Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - BlackRock Total Return V.I. Fund		Class I Shares	Class III Shares
Management Fees	[1],[2]	0.45%	0.45%
Distribution and/or Service (12b-1) Fees		none	0.25%
Other Expenses	[3]	0.49%	0.46%
Interest Expense		0.12%	0.12%
Miscellaneous Other Expenses		0.37%	0.34%
Total Annual Fund Operating Expenses		0.94%	1.16%
Fee Waivers and/or Expense Reimbursements	[1],[4]	(0.20%)	(0.10%)
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	[1],[4]	0.74%	1.06%

Example:

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The Example does not reflect charges imposed by the Contract. See the Contract prospectus for information on such charges. Although your actual costs may be higher or lower, based on these assumptions and the net expenses shown in the fee table, your costs would be:

Expense Example - BlackRock Total Return V.I. Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Class I Shares	76	280	501	1,136
Class III Shares	108	359	629	1,400

Portfolio Turnover:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance.

The Fund has not commenced operations as of the date of this prospectus, but it is expected that BlackRock Total Return V.I. Fund, a series of BlackRock Variable Series Funds, Inc. (the “Predecessor Fund”), will be reorganized into the Fund. During the most recent fiscal year, the Predecessor Fund’s portfolio turnover rate was 627% of the average value of its portfolio.

Principal Investment Strategies of the Fund

The Fund seeks to provide current income by investing in securities that pay interest or dividends. Dividends include exempt interest, ordinary income and capital gains paid to shareholders. Dividends may be reinvested in additional Fund shares as they are paid. The Fund may also seek growth of capital by looking for investments that will increase in value. However, the Fund’s investments emphasize current income more than growth of capital.

The Fund under normal circumstances will invest at least 80%, and typically invests 90% or more, of its assets in fixed-income securities such as corporate bonds and notes, mortgage-backed securities, asset-backed securities, convertible securities, preferred stocks, government obligations and money market securities. Both U.S. and foreign companies and governments may issue these securities, including issuers in emerging markets. The Fund invests primarily in fixed-income securities rated investment grade by a nationally recognized statistical rating organization (“NRSRO”). Fixed-income securities in any of the four highest rating categories can be called “investment grade.” The Fund may also invest in fixed-income securities that are rated below investment grade (commonly called “junk bonds”). The Fund may invest in fixed-income securities of any maturity or duration.

The Fund may invest up to 30% of its net assets in securities of foreign issuers, of which 20% (as a percentage of the Fund’s net assets) may be in emerging markets issuers. Investments in U.S. dollar-denominated securities of foreign issuers, excluding issuers from emerging markets, are permitted beyond the 30% limit. This means that the Fund may invest in such U.S. dollar-denominated securities of foreign issuers without limit. The Fund may enter into reverse repurchase agreements and dollar rolls. The Fund may also invest in derivative instruments, including, but not limited to, interest rate, total return and credit default swaps, indexed and inverse floating rate securities, options, futures, options on futures and swaps, both for hedging purposes and to seek to enhance its returns. The Fund may also invest in credit linked notes, credit linked trust certificates, structured notes, or other instruments evidencing interests in special purpose vehicles, trusts, or other entities that hold or represent interests in fixed-income securities.

The Fund may invest up to 15% of its net assets in collateralized debt obligations (“CDOs”), of which 10% (as a percentage of the Fund’s net assets) may be in collateralized loan obligations (“CLOs”). CDOs are types of asset-backed securities. CLOs are ordinarily issued by a trust or other special purpose entity and are typically collateralized by a pool of loans, which may include, among others, domestic and non-U.S. senior secured loans, senior unsecured loans, and subordinate corporate loans, including loans that may be rated below investment grade or equivalent unrated loans, held by such issuer.

The Fund may engage in active and frequent trading of portfolio securities to seek to achieve its primary investment strategies.

Principal Risks of Investing in the Fund

Risk is inherent in all investing. The value of your investment in the Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund.

• Collateralized Debt Obligations Risk — In addition to the typical risks associated with fixed-income securities and asset-backed securities, CDOs carry additional risks including, but not limited to: (i) the possibility that distributions from collateral securities will not be adequate to make interest or other payments; (ii) the risk that the collateral may default or decline in value or be downgraded, if rated by a nationally recognized statistical rating organization; (iii) the Fund may invest in tranches of CDOs that are subordinate to other tranches; (iv) the structure and complexity of the transaction and the legal documents could lead to disputes among investors regarding the characterization of proceeds; (v) the investment return achieved by the Fund could be significantly different than those predicted by financial models; (vi) the lack of a readily available secondary market for CDOs; (vii) the risk of forced “fire sale” liquidation due to technical defaults such as coverage test failures; and (viii) the CDO’s manager may perform poorly. In addition, investments in CDOs may be characterized by the Fund as illiquid securities.

• Commodities Related Investments Risk — Exposure to the commodities markets may subject the Fund to greater volatility than investments in traditional securities. The value of commodity-linked derivative investments may be affected by changes in overall market movements, commodity index volatility, changes in interest rates, or factors affecting a particular industry or commodity, such as drought, floods, weather, embargoes, tariffs and international economic, political and regulatory developments.

• Convertible Securities Risk — The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest or dividends when due, and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock.

• Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.
  
  Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise. The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management. To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities. These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change. A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
  
  Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.
  
  Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
  
  Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.

• Derivatives Risk — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:
  
  Volatility Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.
  
  Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation.
  
  Market and Liquidity Risk — The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately.
  
  Valuation Risk — Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them.
  
  Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences.
  
  Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments.
  
  Regulatory Risk — Derivative contracts, including, without limitation, swaps, currency forwards and non-deliverable forwards, are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (“Dodd-Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, certain derivatives are subject to margin requirements and swap dealers are required to collect margin from the Fund with respect to such derivatives. Specifically, regulations are now in effect that require swap dealers to post and collect variation margin (comprised of specified liquid instruments and subject to a required haircut) in connection with trading of over-the-counter (“OTC”) swaps with the Fund. Shares of investment companies (other than certain money market funds) may not be posted as collateral under these regulations. Requirements for posting of initial margin in connection with OTC swaps will be phased-in through 2020. In addition, regulations adopted by prudential regulators that will begin to take effect in 2019 will require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Fund, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Fund of trading in these instruments and, as a result, may affect returns to investors in the Fund.

• Dollar Rolls Risk — Dollar rolls involve the risk that the market value of the securities that the Fund is committed to buy may decline below the price of the securities the Fund has sold. These transactions may involve leverage.

• Emerging Markets Risk — Emerging markets are riskier than more developed markets because they tend to develop unevenly and may never fully develop. Investments in emerging markets may be considered speculative. Emerging markets are more likely to experience hyperinflation and currency devaluations, which adversely affect returns to U.S. investors. In addition, many emerging securities markets have far lower trading volumes and less liquidity than developed markets.

• Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include:

• The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight.

• Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio.

• The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position.

• The governments of certain countries may prohibit or impose substantial restrictions on foreign investments in their capital markets or in certain industries.

• Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws.

• Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments.

• The European financial markets have recently experienced volatility and adverse trends due to concerns about economic downturns in, or rising government debt levels of, several European countries. These events may spread to other countries in Europe. These events may affect the value and liquidity of certain of the Fund’s investments.

• High Portfolio Turnover Risk — The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of Fund portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect Fund performance. In addition, investment in mortgage dollar rolls and participation in to-be-announced (“TBA”) transactions may significantly increase the Fund’s portfolio turnover rate. A TBA transaction is a method of trading mortgage-backed securities where the buyer and seller agree upon general trade parameters such as agency, settlement date, par amount, and price at the time the contract is entered into but the mortgage-backed securities are delivered in the future, generally 30 days later.

• Junk Bonds Risk — Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that are considered speculative and may cause income and principal losses for the Fund.

• Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.

• Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.

• Mortgage- and Asset-Backed Securities Risks — Mortgage- and asset-backed securities represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. Mortgage- and asset-backed securities are subject to credit, interest rate, prepayment and extension risks. These securities also are subject to risk of default on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities.

• Preferred Securities Risk — Preferred securities may pay fixed or adjustable rates of return. Preferred securities are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred securities generally pay dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred securities will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. Preferred securities of smaller companies may be more vulnerable to adverse developments than preferred securities of larger companies.

• Reverse Repurchase Agreements Risk — Reverse repurchase agreements involve the sale of securities held by the Fund with an agreement to repurchase the securities at an agreed-upon price, date and interest payment. Reverse repurchase agreements involve the risk that the other party may fail to return the securities in a timely manner or at all. The Fund could lose money if it is unable to recover the securities and the value of the collateral held by the Fund, including the value of the investments made with cash collateral, is less than the value of the securities. These events could also trigger adverse tax consequences to the Fund.

• Sovereign Debt Risk — Sovereign debt instruments are subject to the risk that a governmental entity may delay or refuse to pay interest or repay principal on its sovereign debt, due, for example, to cash flow problems, insufficient foreign currency reserves, political considerations, the relative size of the governmental entity’s debt position in relation to the economy or the failure to put in place economic reforms required by the International Monetary Fund or other multilateral agencies.

• Structured Notes Risk — Structured notes and other related instruments purchased by the Fund are generally privately negotiated debt obligations where the principal and/or interest is determined by reference to the performance of a specific asset, benchmark asset, market or interest rate (“reference measure”). The purchase of structured notes exposes the Fund to the credit risk of the issuer of the structured product. Structured notes may be leveraged, increasing the volatility of each structured note’s value relative to the change in the reference measure. Structured notes may also be less liquid and more difficult to price accurately than less complex securities and instruments or more traditional debt securities.

• U.S. Government Issuer Risk — Treasury obligations may differ in their interest rates, maturities, times of issuance and other characteristics. Obligations of U.S. Government agencies and authorities are supported by varying degrees of credit but generally are not backed by the full faith and credit of the U.S. Government. No assurance can be given that the U.S. Government will provide financial support to its agencies and authorities if it is not obligated by law to do so.

Performance Information

The Fund has not commenced operations as of the date of this prospectus. The returns presented for the Fund reflect the performance of the Predecessor Fund. It is anticipated that on or about September 17, 2018, the Fund will acquire all of the assets, subject to the liabilities, of the Predecessor Fund through a tax-free reorganization (the “Reorganization”). As a result of the Reorganization, the Fund will adopt the performance and financial history of the Predecessor Fund. The Reorganization is being consummated in connection with a potential reconfiguration of the existing fund complexes overseen by the boards of directors/trustees of the BlackRock-advised funds. The Fund has the same investment objectives, strategies and policies, portfolio management team and contractual arrangements, including the same contractual fees and expenses, as the Predecessor Fund. As a result, the performance of the Fund would have been substantially similar to that of the Predecessor Fund.

The information shows you how the Predecessor Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The table compares the Predecessor Fund’s performance to that of the Bloomberg Barclays U.S. Aggregate Bond Index. As with all such investments, past performance is not an indication of future results. The bar chart and table do not reflect separate account fees and expenses. If they did, returns would be less than those shown. The returns for Class III Shares prior to August 14, 2012, the recommencement of operations of Class III Shares, are based upon performance of the Predecessor Fund’s Class I Shares, as adjusted to reflect the distribution and/or service (12b-1) fees applicable to Class III Shares. This information may be considered when assessing the performance of Class III Shares, but does not represent the actual performance of Class III Shares. To the extent that dividends and distributions have been paid by the Predecessor Fund, the performance information for the Predecessor Fund in the chart and table assumes reinvestment of the dividends and distributions. If the Predecessor Fund’s investment manager and its affiliates had not waived or reimbursed certain Predecessor Fund expenses during these periods, the Predecessor Fund’s returns would have been lower.

Class I Shares
ANNUAL TOTAL RETURNS
BlackRock Total Return V.I. Fund
As of 12/31

During the ten-year period shown in the bar chart, the highest return for a quarter was 8.20% (quarter ended September 30, 2009) and the lowest return for a quarter was -7.01% (quarter ended September 30, 2008).

As of 12/31/17
Average Annual Total Returns

Average Annual Total Returns - BlackRock Total Return V.I. Fund	1 Year	5 Years	10 Years
Class I Shares	3.60%	2.39%	3.91%
Class III Shares	3.21%	2.08%	3.61%
Bloomberg Barclays U.S. Aggregate Bond Index (Reflects no deduction for fees, expenses or taxes)	3.54%	2.10%	4.01%

[1] As described in the “Management of the Funds” section of the Fund’s prospectus, BlackRock Advisors, LLC (“BlackRock”) has contractually agreed to waive the management fee with respect to any portion of the Fund’s assets estimated to be attributable to investments in other equity and fixed-income mutual funds and exchange-traded funds managed by BlackRock or its affiliates that have a contractual management fee, through April 30, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of BlackRock Variable Series Funds II, Inc. (the “Company”) or by a vote of a majority of the outstanding voting securities of the Fund.

[2] Management Fee is based on the management fee rate of the Predecessor Fund (defined below).

[3] Other Expenses are based on estimated amounts for the current fiscal year, which are based on the expenses of the Predecessor Fund for its most recent fiscal year.

[4] As described in the “Management of the Funds” section of the Fund’s prospectus, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 1.25% (for Class I Shares) and 1.50% (for Class III Shares) of average daily net assets through April 30, 2020. BlackRock has also contractually agreed to reimburse fees in order to limit certain operational and recordkeeping fees to 0% (for Class I Shares) and 0.06% (for Class III Shares) of average daily net assets through April 30, 2020. Each of these contractual agreements may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Company or by a vote of a majority of the outstanding voting securities of the Fund.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	BlackRock Variable Series Funds II, Inc.
Prospectus Date	rr_ProspectusDate	Jul. 02, 2018
BlackRock Total Return V.I. Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Overview Key Facts About BlackRock Total Return V.I. Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the BlackRock Total Return V.I. Fund (the “Fund”) is to maximize total return, consistent with income generation and prudent investment management.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses of the Fund
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. The expenses below do not include separate account fees and expenses, and would be higher if these fees and expenses were included. Please refer to your variable annuity or insurance contract (the “Contract”) prospectus for information on the separate account fees and expenses associated with your Contract.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment) The Fund is not subject to any shareholder fees.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	April 30, 2020
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. The Fund has not commenced operations as of the date of this prospectus, but it is expected that BlackRock Total Return V.I. Fund, a series of BlackRock Variable Series Funds, Inc. (the “Predecessor Fund”), will be reorganized into the Fund. During the most recent fiscal year, the Predecessor Fund’s portfolio turnover rate was 627% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	627.00%
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year, which are based on the expenses of the Predecessor Fund for its most recent fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	Example:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The Example does not reflect charges imposed by the Contract. See the Contract prospectus for information on such charges. Although your actual costs may be higher or lower, based on these assumptions and the net expenses shown in the fee table, your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies of the Fund
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund seeks to provide current income by investing in securities that pay interest or dividends. Dividends include exempt interest, ordinary income and capital gains paid to shareholders. Dividends may be reinvested in additional Fund shares as they are paid. The Fund may also seek growth of capital by looking for investments that will increase in value. However, the Fund’s investments emphasize current income more than growth of capital. The Fund under normal circumstances will invest at least 80%, and typically invests 90% or more, of its assets in fixed-income securities such as corporate bonds and notes, mortgage-backed securities, asset-backed securities, convertible securities, preferred stocks, government obligations and money market securities. Both U.S. and foreign companies and governments may issue these securities, including issuers in emerging markets. The Fund invests primarily in fixed-income securities rated investment grade by a nationally recognized statistical rating organization (“NRSRO”). Fixed-income securities in any of the four highest rating categories can be called “investment grade.” The Fund may also invest in fixed-income securities that are rated below investment grade (commonly called “junk bonds”). The Fund may invest in fixed-income securities of any maturity or duration. The Fund may invest up to 30% of its net assets in securities of foreign issuers, of which 20% (as a percentage of the Fund’s net assets) may be in emerging markets issuers. Investments in U.S. dollar-denominated securities of foreign issuers, excluding issuers from emerging markets, are permitted beyond the 30% limit. This means that the Fund may invest in such U.S. dollar-denominated securities of foreign issuers without limit. The Fund may enter into reverse repurchase agreements and dollar rolls. The Fund may also invest in derivative instruments, including, but not limited to, interest rate, total return and credit default swaps, indexed and inverse floating rate securities, options, futures, options on futures and swaps, both for hedging purposes and to seek to enhance its returns. The Fund may also invest in credit linked notes, credit linked trust certificates, structured notes, or other instruments evidencing interests in special purpose vehicles, trusts, or other entities that hold or represent interests in fixed-income securities. The Fund may invest up to 15% of its net assets in collateralized debt obligations (“CDOs”), of which 10% (as a percentage of the Fund’s net assets) may be in collateralized loan obligations (“CLOs”). CDOs are types of asset-backed securities. CLOs are ordinarily issued by a trust or other special purpose entity and are typically collateralized by a pool of loans, which may include, among others, domestic and non-U.S. senior secured loans, senior unsecured loans, and subordinate corporate loans, including loans that may be rated below investment grade or equivalent unrated loans, held by such issuer. The Fund may engage in active and frequent trading of portfolio securities to seek to achieve its primary investment strategies.
Risk [Heading]	rr_RiskHeading	Principal Risks of Investing in the Fund
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Risk is inherent in all investing. The value of your investment in the Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund. Collateralized Debt Obligations Risk — In addition to the typical risks associated with fixed-income securities and asset-backed securities, CDOs carry additional risks including, but not limited to: (i) the possibility that distributions from collateral securities will not be adequate to make interest or other payments; (ii) the risk that the collateral may default or decline in value or be downgraded, if rated by a nationally recognized statistical rating organization; (iii) the Fund may invest in tranches of CDOs that are subordinate to other tranches; (iv) the structure and complexity of the transaction and the legal documents could lead to disputes among investors regarding the characterization of proceeds; (v) the investment return achieved by the Fund could be significantly different than those predicted by financial models; (vi) the lack of a readily available secondary market for CDOs; (vii) the risk of forced “fire sale” liquidation due to technical defaults such as coverage test failures; and (viii) the CDO’s manager may perform poorly. In addition, investments in CDOs may be characterized by the Fund as illiquid securities. Commodities Related Investments Risk — Exposure to the commodities markets may subject the Fund to greater volatility than investments in traditional securities. The value of commodity-linked derivative investments may be affected by changes in overall market movements, commodity index volatility, changes in interest rates, or factors affecting a particular industry or commodity, such as drought, floods, weather, embargoes, tariffs and international economic, political and regulatory developments. Convertible Securities Risk — The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest or dividends when due, and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock. Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things. Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise. The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management. To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities. These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change. A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance. Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation. Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall. Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields. Derivatives Risk — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including: Volatility Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets. Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation. Market and Liquidity Risk — The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately. Valuation Risk — Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them. Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences. Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments. Regulatory Risk — Derivative contracts, including, without limitation, swaps, currency forwards and non-deliverable forwards, are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (“Dodd-Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, certain derivatives are subject to margin requirements and swap dealers are required to collect margin from the Fund with respect to such derivatives. Specifically, regulations are now in effect that require swap dealers to post and collect variation margin (comprised of specified liquid instruments and subject to a required haircut) in connection with trading of over-the-counter (“OTC”) swaps with the Fund. Shares of investment companies (other than certain money market funds) may not be posted as collateral under these regulations. Requirements for posting of initial margin in connection with OTC swaps will be phased-in through 2020. In addition, regulations adopted by prudential regulators that will begin to take effect in 2019 will require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Fund, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Fund of trading in these instruments and, as a result, may affect returns to investors in the Fund. Dollar Rolls Risk — Dollar rolls involve the risk that the market value of the securities that the Fund is committed to buy may decline below the price of the securities the Fund has sold. These transactions may involve leverage. Emerging Markets Risk — Emerging markets are riskier than more developed markets because they tend to develop unevenly and may never fully develop. Investments in emerging markets may be considered speculative. Emerging markets are more likely to experience hyperinflation and currency devaluations, which adversely affect returns to U.S. investors. In addition, many emerging securities markets have far lower trading volumes and less liquidity than developed markets. Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include: The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight. Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio. The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position. The governments of certain countries may prohibit or impose substantial restrictions on foreign investments in their capital markets or in certain industries. Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws. Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments. The European financial markets have recently experienced volatility and adverse trends due to concerns about economic downturns in, or rising government debt levels of, several European countries. These events may spread to other countries in Europe. These events may affect the value and liquidity of certain of the Fund’s investments. High Portfolio Turnover Risk — The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of Fund portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect Fund performance. In addition, investment in mortgage dollar rolls and participation in to-be-announced (“TBA”) transactions may significantly increase the Fund’s portfolio turnover rate. A TBA transaction is a method of trading mortgage-backed securities where the buyer and seller agree upon general trade parameters such as agency, settlement date, par amount, and price at the time the contract is entered into but the mortgage-backed securities are delivered in the future, generally 30 days later. Junk Bonds Risk — Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that are considered speculative and may cause income and principal losses for the Fund. Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage. Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money. Mortgage- and Asset-Backed Securities Risks — Mortgage- and asset-backed securities represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. Mortgage- and asset-backed securities are subject to credit, interest rate, prepayment and extension risks. These securities also are subject to risk of default on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities. Preferred Securities Risk — Preferred securities may pay fixed or adjustable rates of return. Preferred securities are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred securities generally pay dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred securities will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. Preferred securities of smaller companies may be more vulnerable to adverse developments than preferred securities of larger companies. Reverse Repurchase Agreements Risk — Reverse repurchase agreements involve the sale of securities held by the Fund with an agreement to repurchase the securities at an agreed-upon price, date and interest payment. Reverse repurchase agreements involve the risk that the other party may fail to return the securities in a timely manner or at all. The Fund could lose money if it is unable to recover the securities and the value of the collateral held by the Fund, including the value of the investments made with cash collateral, is less than the value of the securities. These events could also trigger adverse tax consequences to the Fund. Sovereign Debt Risk — Sovereign debt instruments are subject to the risk that a governmental entity may delay or refuse to pay interest or repay principal on its sovereign debt, due, for example, to cash flow problems, insufficient foreign currency reserves, political considerations, the relative size of the governmental entity’s debt position in relation to the economy or the failure to put in place economic reforms required by the International Monetary Fund or other multilateral agencies. Structured Notes Risk — Structured notes and other related instruments purchased by the Fund are generally privately negotiated debt obligations where the principal and/or interest is determined by reference to the performance of a specific asset, benchmark asset, market or interest rate (“reference measure”). The purchase of structured notes exposes the Fund to the credit risk of the issuer of the structured product. Structured notes may be leveraged, increasing the volatility of each structured note’s value relative to the change in the reference measure. Structured notes may also be less liquid and more difficult to price accurately than less complex securities and instruments or more traditional debt securities. U.S. Government Issuer Risk — Treasury obligations may differ in their interest rates, maturities, times of issuance and other characteristics. Obligations of U.S. Government agencies and authorities are supported by varying degrees of credit but generally are not backed by the full faith and credit of the U.S. Government. No assurance can be given that the U.S. Government will provide financial support to its agencies and authorities if it is not obligated by law to do so.
Risk Lose Money [Text]	rr_RiskLoseMoney	You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not commenced operations as of the date of this prospectus. The returns presented for the Fund reflect the performance of the Predecessor Fund. It is anticipated that on or about September 17, 2018, the Fund will acquire all of the assets, subject to the liabilities, of the Predecessor Fund through a tax-free reorganization (the “Reorganization”). As a result of the Reorganization, the Fund will adopt the performance and financial history of the Predecessor Fund. The Reorganization is being consummated in connection with a potential reconfiguration of the existing fund complexes overseen by the boards of directors/trustees of the BlackRock-advised funds. The Fund has the same investment objectives, strategies and policies, portfolio management team and contractual arrangements, including the same contractual fees and expenses, as the Predecessor Fund. As a result, the performance of the Fund would have been substantially similar to that of the Predecessor Fund. The information shows you how the Predecessor Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The table compares the Predecessor Fund’s performance to that of the Bloomberg Barclays U.S. Aggregate Bond Index. As with all such investments, past performance is not an indication of future results. The bar chart and table do not reflect separate account fees and expenses. If they did, returns would be less than those shown. The returns for Class III Shares prior to August 14, 2012, the recommencement of operations of Class III Shares, are based upon performance of the Predecessor Fund’s Class I Shares, as adjusted to reflect the distribution and/or service (12b-1) fees applicable to Class III Shares. This information may be considered when assessing the performance of Class III Shares, but does not represent the actual performance of Class III Shares. To the extent that dividends and distributions have been paid by the Predecessor Fund, the performance information for the Predecessor Fund in the chart and table assumes reinvestment of the dividends and distributions. If the Predecessor Fund’s investment manager and its affiliates had not waived or reimbursed certain Predecessor Fund expenses during these periods, the Predecessor Fund’s returns would have been lower.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The information shows you how the Predecessor Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund.
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	As with all such investments, past performance is not an indication of future results.
Bar Chart [Heading]	rr_BarChartHeading	Class I Shares ANNUAL TOTAL RETURNS BlackRock Total Return V.I. Fund As of 12/31
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The bar chart and table do not reflect separate account fees and expenses. If they did, returns would be less than those shown.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the ten-year period shown in the bar chart, the highest return for a quarter was 8.20% (quarter ended September 30, 2009) and the lowest return for a quarter was -7.01% (quarter ended September 30, 2008).
Performance Table Heading	rr_PerformanceTableHeading	As of 12/31/17 Average Annual Total Returns
BlackRock Total Return V.I. Fund | Class I Shares
Risk/Return:	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.45%	[1],[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Interest Expense	rr_Component1OtherExpensesOverAssets	0.12%
Miscellaneous Other Expenses	rr_Component2OtherExpensesOverAssets	0.37%
Other Expenses	rr_OtherExpensesOverAssets	0.49%	[3]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.94%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.20%)	[1],[4]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.74%	[1],[4]
1 Year	rr_ExpenseExampleYear01	$ 76
3 Years	rr_ExpenseExampleYear03	280
5 Years	rr_ExpenseExampleYear05	501
10 Years	rr_ExpenseExampleYear10	$ 1,136
2008	rr_AnnualReturn2008	(12.13%)
2009	rr_AnnualReturn2009	17.79%
2010	rr_AnnualReturn2010	9.69%
2011	rr_AnnualReturn2011	6.07%
2012	rr_AnnualReturn2012	8.25%
2013	rr_AnnualReturn2013	(1.14%)
2014	rr_AnnualReturn2014	6.66%
2015	rr_AnnualReturn2015	0.26%
2016	rr_AnnualReturn2016	2.76%
2017	rr_AnnualReturn2017	3.60%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	8.20%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(7.01%)
1 Year	rr_AverageAnnualReturnYear01	3.60%
5 Years	rr_AverageAnnualReturnYear05	2.39%
10 Years	rr_AverageAnnualReturnYear10	3.91%
BlackRock Total Return V.I. Fund | Class III Shares
Risk/Return:	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.45%	[1],[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Interest Expense	rr_Component1OtherExpensesOverAssets	0.12%
Miscellaneous Other Expenses	rr_Component2OtherExpensesOverAssets	0.34%
Other Expenses	rr_OtherExpensesOverAssets	0.46%	[3]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.16%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.10%)	[1],[4]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.06%	[1],[4]
1 Year	rr_ExpenseExampleYear01	$ 108
3 Years	rr_ExpenseExampleYear03	359
5 Years	rr_ExpenseExampleYear05	629
10 Years	rr_ExpenseExampleYear10	$ 1,400
1 Year	rr_AverageAnnualReturnYear01	3.21%
5 Years	rr_AverageAnnualReturnYear05	2.08%
10 Years	rr_AverageAnnualReturnYear10	3.61%
BlackRock Total Return V.I. Fund | Bloomberg Barclays U.S. Aggregate Bond Index (Reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	3.54%
5 Years	rr_AverageAnnualReturnYear05	2.10%
10 Years	rr_AverageAnnualReturnYear10	4.01%

[1] As described in the “Management of the Funds” section of the Fund’s prospectus, BlackRock Advisors, LLC (“BlackRock”) has contractually agreed to waive the management fee with respect to any portion of the Fund’s assets estimated to be attributable to investments in other equity and fixed-income mutual funds and exchange-traded funds managed by BlackRock or its affiliates that have a contractual management fee, through April 30, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of BlackRock Variable Series Funds II, Inc. (the “Company”) or by a vote of a majority of the outstanding voting securities of the Fund.

[2] Management Fee is based on the management fee rate of the Predecessor Fund (defined below).

[3] Other Expenses are based on estimated amounts for the current fiscal year, which are based on the expenses of the Predecessor Fund for its most recent fiscal year.

[4] As described in the “Management of the Funds” section of the Fund’s prospectus, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 1.25% (for Class I Shares) and 1.50% (for Class III Shares) of average daily net assets through April 30, 2020. BlackRock has also contractually agreed to reimburse fees in order to limit certain operational and recordkeeping fees to 0% (for Class I Shares) and 0.06% (for Class III Shares) of average daily net assets through April 30, 2020. Each of these contractual agreements may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Company or by a vote of a majority of the outstanding voting securities of the Fund.

XML

BlackRock U.S. Government Bond V.I. Fund

Fund Overview

Key Facts About BlackRock U.S. Government Bond V.I. Fund

Investment Objective

The investment objective of the BlackRock U.S. Government Bond V.I. Fund (the “Fund”) is to seek to maximize total return, consistent with income generation and prudent investment management.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. The expenses below do not include separate account fees and expenses, and would be higher if these fees and expenses were included. Please refer to your variable annuity or insurance contract (the “Contract”) prospectus for information on the separate account fees and expenses associated with your Contract.

Shareholder Fees (fees paid directly from your investment)

The Fund is not subject to any shareholder fees.

Annual Fund Operating Expenses
(expenses that you pay each year as a
percentage of the value of your investment)

Annual Fund Operating Expenses - BlackRock U.S. Government Bond V.I. Fund		Class I Shares	Class III Shares
Management Fees	[1],[2]	0.50%	0.50%
Distribution and/or Service (12b-1) Fees		none	0.25%
Other Expenses	[3]	0.81%	0.70%
Interest Expense		0.14%	0.14%
Miscellaneous Other Expenses		0.67%	0.56%
Total Annual Fund Operating Expenses		1.31%	1.45%
Fee Waivers and/or Expense Reimbursements	[1],[4]	(0.20%)	(0.05%)
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	[1],[4]	1.11%	1.40%

Example:

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The Example does not reflect charges imposed by the Contract. See the Contract prospectus for information on such charges. Although your actual costs may be higher or lower, based on these assumptions and the net expenses shown in the fee table, your costs would be:

Expense Example - BlackRock U.S. Government Bond V.I. Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Class I Shares	113	395	699	1,562
Class III Shares	143	454	787	1,731

Portfolio Turnover:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance.

The Fund has not commenced operations as of the date of this prospectus, but it is expected that BlackRock U.S. Government Bond V.I. Fund, a series of BlackRock Variable Series Funds, Inc. (the “Predecessor Fund”), will be reorganized into the Fund. During the most recent fiscal year, the Predecessor Fund’s portfolio turnover rate was 1052% of the average value of its portfolio.

Principal Investment Strategies of the Fund

Under normal circumstances, the Fund invests at least 80% of its assets in bonds that are issued or guaranteed by the U.S. Government and its agencies. The Fund invests primarily in the highest rated government and agency bonds and maintains an average portfolio duration that is within ±20% of the Bloomberg Barclays U.S. Government/Mortgage Index (the benchmark).

Securities purchased by the Fund (except with respect to non-dollar denominated bonds) generally are rated in the highest rating category (AAA or Aaa) at the time of purchase by at least one major rating agency or are determined by the Fund management team to be of similar quality. The Fund may also invest up to 5% of its assets in dollar-denominated investment grade securities that are rated below the highest rating category at the time of purchase. In addition, the Fund’s dollar-weighted average maturity will be between 3 and 10 years.

The Fund evaluates sectors of the bond market and individual securities within these sectors. The Fund selects bonds from several sectors including: U.S. Treasuries and agency securities, commercial and residential mortgage-backed securities, collateralized mortgage obligations (“CMOs”), asset-backed securities and corporate bonds.

The Fund invests primarily in dollar-denominated bonds, but may invest up to 10% of its assets in non-dollar denominated bonds of issuers located outside of the United States. The Fund’s investment in non-dollar denominated bonds may be on a currency hedged or unhedged basis. Non-dollar denominated bonds purchased by the Fund are, at the time of purchase, rated in the four highest rating categories by at least one major rating agency (Baa or better by Moody’s Investors Service, Inc. (“Moody’s”) or BBB or better by S&P Global Ratings (“S&P”) or Fitch Ratings Inc. (“Fitch”)) or are determined by the Fund management team to be of similar quality. Securities rated in any of the four highest rating categories are known as “investment grade” securities.

The Fund may buy or sell options or futures on a security or an index of securities, or enter into credit default swaps and interest rate or foreign currency transactions, including swaps (collectively, commonly known as derivatives). The Fund may seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as reverse repurchase agreements or dollar rolls).

The Fund may engage in active and frequent trading of portfolio securities to achieve its primary investment strategies.

Principal Risks of Investing in the Fund

Risk is inherent in all investing. The value of your investment in the Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund.

• Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.
  
  Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise. The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management. To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities. These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change. A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
  
  Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.
  
  Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
  
  Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.
  
  Derivatives Risk — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:
  
  Volatility Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.
  
  Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation.
  
  Market and Liquidity Risk — The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately.
  
  Valuation Risk — Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them.
  
  Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences.
  
  Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments.
  
  Regulatory Risk — Derivative contracts, including, without limitation, swaps, currency forwards and non-deliverable forwards, are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (“Dodd-Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, certain derivatives are subject to margin requirements and swap dealers are required to collect margin from the Fund with respect to such derivatives. Specifically, regulations are now in effect that require swap dealers to post and collect variation margin (comprised of specified liquid instruments and subject to a required haircut) in connection with trading of over-the-counter (“OTC”) swaps with the Fund. Shares of investment companies (other than certain money market funds) may not be posted as collateral under these regulations. Requirements for posting of initial margin in connection with OTC swaps will be phased-in through 2020. In addition, regulations adopted by prudential regulators that will begin to take effect in 2019 will require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Fund, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Fund of trading in these instruments and, as a result, may affect returns to investors in the Fund.

• Dollar Rolls Risk — Dollar rolls involve the risk that the market value of the securities that the Fund is committed to buy may decline below the price of the securities the Fund has sold. These transactions may involve leverage.

• Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include:

• The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight.

• Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio.

• The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position.

• The governments of certain countries may prohibit or impose substantial restrictions on foreign investments in their capital markets or in certain industries.

• Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws.

• Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments.

• High Portfolio Turnover Risk — The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of Fund portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect Fund performance. In addition, investment in mortgage dollar rolls and participation in to-be-announced (“TBA”) transactions may significantly increase the Fund’s portfolio turnover rate. A TBA transaction is a method of trading mortgage-backed securities where the buyer and seller agree upon general trade parameters such as agency, settlement date, par amount, and price at the time the contract is entered into but the mortgage-backed securities are delivered in the future, generally 30 days later.

• Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.

• Liquidity Risk — Liquidity risk exists when particular investments are difficult to purchase or sell. The Fund’s investments in illiquid securities may reduce the returns of the Fund because it may be difficult to sell the illiquid securities at an advantageous time or price. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to liquidity risk. Liquidity risk may be the result of, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active market. Liquid investments may become illiquid or less liquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid and relatively less liquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. This may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed-income mutual funds may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions.

• Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.

• Mortgage- and Asset-Backed Securities Risks — Mortgage- and asset-backed securities represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. Mortgage- and asset-backed securities are subject to credit, interest rate, prepayment and extension risks. These securities also are subject to risk of default on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities.

• Repurchase Agreements and Purchase and Sale Contracts Risk — If the other party to a repurchase agreement or purchase and sale contract defaults on its obligation under the agreement, the Fund may suffer delays and incur costs or lose money in exercising its rights under the agreement. If the seller fails to repurchase the security in either situation and the market value of the security declines, the Fund may lose money.

• Reverse Repurchase Agreements Risk — Reverse repurchase agreements involve the sale of securities held by the Fund with an agreement to repurchase the securities at an agreed-upon price, date and interest payment. Reverse repurchase agreements involve the risk that the other party may fail to return the securities in a timely manner or at all. The Fund could lose money if it is unable to recover the securities and the value of the collateral held by the Fund, including the value of the investments made with cash collateral, is less than the value of the securities. These events could also trigger adverse tax consequences to the Fund.

• U.S. Government Issuer Risk — Treasury obligations may differ in their interest rates, maturities, times of issuance and other characteristics. Obligations of U.S. Government agencies and authorities are supported by varying degrees of credit but generally are not backed by the full faith and credit of the U.S. Government. No assurance can be given that the U.S. Government will provide financial support to its agencies and authorities if it is not obligated by law to do so.

Performance Information

The Fund has not commenced operations as of the date of this prospectus. The returns presented for the Fund reflect the performance of the Predecessor Fund. It is anticipated that on or about September 17, 2018, the Fund will acquire all of the assets, subject to the liabilities, of the Predecessor Fund through a tax-free reorganization (the “Reorganization”). As a result of the Reorganization, the Fund will adopt the performance and financial history of the Predecessor Fund. The Reorganization is being consummated in connection with a potential reconfiguration of the existing fund complexes overseen by the boards of directors/trustees of the BlackRock-advised funds. The Fund has the same investment objectives, strategies and policies, portfolio management team and contractual arrangements, including the same contractual fees and expenses, as the Predecessor Fund. As a result, the performance of the Fund would have been substantially similar to that of the Predecessor Fund.

The information shows you how the Predecessor Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The Predecessor Fund’s returns prior to October 1, 2011 as reflected in the bar chart and the table are the returns of a fund that followed different investment objectives and investment strategies under the name “BlackRock Government Income V.I. Fund.” The table compares the Predecessor Fund’s performance to that of the Bloomberg Barclays U.S. Government/Mortgage Index and the Bloomberg Barclays U.S. Mortgage-Backed Securities Index, which are relevant to the Fund because they have characteristics similar to the Fund’s investment strategies. The bar chart and table do not reflect separate account fees and expenses. If they did, returns would be less than those shown. The returns for Class III Shares prior to July 15, 2013, the recommencement of operations of the Class III Shares, are based upon performance of the Predecessor Fund’s Class I Shares, as adjusted to reflect the distribution and/or service (12b-1) fees applicable to Class III Shares. This information may be considered when assessing the performance of Class III Shares, but does not represent the actual performance of Class III Shares. To the extent that dividends and distributions have been paid by the Predecessor Fund, the performance information for the Predecessor Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance is not an indication of future results. If the Predecessor Fund’s investment manager and its affiliates had not waived or reimbursed certain Predecessor Fund expenses during these periods, the Predecessor Fund’s returns would have been lower.

Class I Shares
ANNUAL TOTAL RETURNS
BlackRock U.S. Government Bond V.I. Fund
As of 12/31

During the ten-year period shown in the bar chart, the highest return for a quarter was 7.73% (quarter ended December 31, 2008) and the lowest return for a quarter was -3.70% (quarter ended June 30, 2008).

As of 12/31/17
Average Annual Total Returns

Average Annual Total Returns - BlackRock U.S. Government Bond V.I. Fund	1 Year	5 Years	10 Years
Class I Shares	1.52%	1.14%	2.86%
Class III Shares	1.10%	0.85%	2.59%
Bloomberg Barclays U.S. Government/Mortgage Index (Reflects no deduction for fees, expenses or taxes)	2.37%	1.59%	3.51%
Bloomberg Barclays U.S. Mortgage-Backed Securities Index (Reflects no deduction for fees, expenses or taxes)	2.47%	2.04%	3.84%

[1] As described in the “Management of the Funds” section of the Fund’s prospectus, BlackRock Advisors, LLC (“BlackRock”) has contractually agreed to waive the management fee with respect to any portion of the Fund’s assets estimated to be attributable to investments in other equity and fixed-income mutual funds and exchange-traded funds managed by BlackRock or its affiliates that have a contractual management fee, through April 30, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of BlackRock Variable Series Funds II, Inc. (the “Company”) or by a vote of a majority of the outstanding voting securities of the Fund.

[2] Management Fee is based on the management fee rate of the Predecessor Fund (defined below).

[3] Other Expenses are based on estimated amounts for the current fiscal year, which are based on the expenses of the Predecessor Fund for its most recent fiscal year.

[4] As described in the “Management of the Funds” section of the Fund’s prospectus, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 1.25% (for Class I Shares) and 1.50% (for Class III Shares) of average daily net assets through April 30, 2020. BlackRock has also contractually agreed to reimburse fees in order to limit certain operational and recordkeeping fees to 0% (for Class I Shares) and 0.06% (for Class III Shares) of average daily net assets through April 30, 2020. Each of these contractual agreements may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Company or by a vote of a majority of the outstanding voting securities of the Fund.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	BlackRock Variable Series Funds II, Inc.
Prospectus Date	rr_ProspectusDate	Jul. 02, 2018
BlackRock U.S. Government Bond V.I. Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Overview Key Facts About BlackRock U.S. Government Bond V.I. Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the BlackRock U.S. Government Bond V.I. Fund (the “Fund”) is to seek to maximize total return, consistent with income generation and prudent investment management.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses of the Fund
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. The expenses below do not include separate account fees and expenses, and would be higher if these fees and expenses were included. Please refer to your variable annuity or insurance contract (the “Contract”) prospectus for information on the separate account fees and expenses associated with your Contract.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment) The Fund is not subject to any shareholder fees.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	April 30, 2020
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. The Fund has not commenced operations as of the date of this prospectus, but it is expected that BlackRock U.S. Government Bond V.I. Fund, a series of BlackRock Variable Series Funds, Inc. (the “Predecessor Fund”), will be reorganized into the Fund. During the most recent fiscal year, the Predecessor Fund’s portfolio turnover rate was 1052% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	1052.00%
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year, which are based on the expenses of the Predecessor Fund for its most recent fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	Example:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The Example does not reflect charges imposed by the Contract. See the Contract prospectus for information on such charges. Although your actual costs may be higher or lower, based on these assumptions and the net expenses shown in the fee table, your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies of the Fund
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests at least 80% of its assets in bonds that are issued or guaranteed by the U.S. Government and its agencies. The Fund invests primarily in the highest rated government and agency bonds and maintains an average portfolio duration that is within ±20% of the Bloomberg Barclays U.S. Government/Mortgage Index (the benchmark). Securities purchased by the Fund (except with respect to non-dollar denominated bonds) generally are rated in the highest rating category (AAA or Aaa) at the time of purchase by at least one major rating agency or are determined by the Fund management team to be of similar quality. The Fund may also invest up to 5% of its assets in dollar-denominated investment grade securities that are rated below the highest rating category at the time of purchase. In addition, the Fund’s dollar-weighted average maturity will be between 3 and 10 years. The Fund evaluates sectors of the bond market and individual securities within these sectors. The Fund selects bonds from several sectors including: U.S. Treasuries and agency securities, commercial and residential mortgage-backed securities, collateralized mortgage obligations (“CMOs”), asset-backed securities and corporate bonds. The Fund invests primarily in dollar-denominated bonds, but may invest up to 10% of its assets in non-dollar denominated bonds of issuers located outside of the United States. The Fund’s investment in non-dollar denominated bonds may be on a currency hedged or unhedged basis. Non-dollar denominated bonds purchased by the Fund are, at the time of purchase, rated in the four highest rating categories by at least one major rating agency (Baa or better by Moody’s Investors Service, Inc. (“Moody’s”) or BBB or better by S&P Global Ratings (“S&P”) or Fitch Ratings Inc. (“Fitch”)) or are determined by the Fund management team to be of similar quality. Securities rated in any of the four highest rating categories are known as “investment grade” securities. The Fund may buy or sell options or futures on a security or an index of securities, or enter into credit default swaps and interest rate or foreign currency transactions, including swaps (collectively, commonly known as derivatives). The Fund may seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as reverse repurchase agreements or dollar rolls). The Fund may engage in active and frequent trading of portfolio securities to achieve its primary investment strategies.
Risk [Heading]	rr_RiskHeading	Principal Risks of Investing in the Fund
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Risk is inherent in all investing. The value of your investment in the Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund. Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things. Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise. The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management. To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities. These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change. A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance. Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation. Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall. Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields. Derivatives Risk — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including: Volatility Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets. Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation. Market and Liquidity Risk — The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately. Valuation Risk — Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them. Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences. Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments. Regulatory Risk — Derivative contracts, including, without limitation, swaps, currency forwards and non-deliverable forwards, are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (“Dodd-Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, certain derivatives are subject to margin requirements and swap dealers are required to collect margin from the Fund with respect to such derivatives. Specifically, regulations are now in effect that require swap dealers to post and collect variation margin (comprised of specified liquid instruments and subject to a required haircut) in connection with trading of over-the-counter (“OTC”) swaps with the Fund. Shares of investment companies (other than certain money market funds) may not be posted as collateral under these regulations. Requirements for posting of initial margin in connection with OTC swaps will be phased-in through 2020. In addition, regulations adopted by prudential regulators that will begin to take effect in 2019 will require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Fund, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Fund of trading in these instruments and, as a result, may affect returns to investors in the Fund. Dollar Rolls Risk — Dollar rolls involve the risk that the market value of the securities that the Fund is committed to buy may decline below the price of the securities the Fund has sold. These transactions may involve leverage. Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include: The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight. Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio. The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position. The governments of certain countries may prohibit or impose substantial restrictions on foreign investments in their capital markets or in certain industries. Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws. Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments. High Portfolio Turnover Risk — The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of Fund portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect Fund performance. In addition, investment in mortgage dollar rolls and participation in to-be-announced (“TBA”) transactions may significantly increase the Fund’s portfolio turnover rate. A TBA transaction is a method of trading mortgage-backed securities where the buyer and seller agree upon general trade parameters such as agency, settlement date, par amount, and price at the time the contract is entered into but the mortgage-backed securities are delivered in the future, generally 30 days later. Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage. Liquidity Risk — Liquidity risk exists when particular investments are difficult to purchase or sell. The Fund’s investments in illiquid securities may reduce the returns of the Fund because it may be difficult to sell the illiquid securities at an advantageous time or price. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to liquidity risk. Liquidity risk may be the result of, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active market. Liquid investments may become illiquid or less liquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid and relatively less liquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. This may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed-income mutual funds may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions. Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money. Mortgage- and Asset-Backed Securities Risks — Mortgage- and asset-backed securities represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. Mortgage- and asset-backed securities are subject to credit, interest rate, prepayment and extension risks. These securities also are subject to risk of default on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities. Repurchase Agreements and Purchase and Sale Contracts Risk — If the other party to a repurchase agreement or purchase and sale contract defaults on its obligation under the agreement, the Fund may suffer delays and incur costs or lose money in exercising its rights under the agreement. If the seller fails to repurchase the security in either situation and the market value of the security declines, the Fund may lose money. Reverse Repurchase Agreements Risk — Reverse repurchase agreements involve the sale of securities held by the Fund with an agreement to repurchase the securities at an agreed-upon price, date and interest payment. Reverse repurchase agreements involve the risk that the other party may fail to return the securities in a timely manner or at all. The Fund could lose money if it is unable to recover the securities and the value of the collateral held by the Fund, including the value of the investments made with cash collateral, is less than the value of the securities. These events could also trigger adverse tax consequences to the Fund. U.S. Government Issuer Risk — Treasury obligations may differ in their interest rates, maturities, times of issuance and other characteristics. Obligations of U.S. Government agencies and authorities are supported by varying degrees of credit but generally are not backed by the full faith and credit of the U.S. Government. No assurance can be given that the U.S. Government will provide financial support to its agencies and authorities if it is not obligated by law to do so.
Risk Lose Money [Text]	rr_RiskLoseMoney	You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not commenced operations as of the date of this prospectus. The returns presented for the Fund reflect the performance of the Predecessor Fund. It is anticipated that on or about September 17, 2018, the Fund will acquire all of the assets, subject to the liabilities, of the Predecessor Fund through a tax-free reorganization (the “Reorganization”). As a result of the Reorganization, the Fund will adopt the performance and financial history of the Predecessor Fund. The Reorganization is being consummated in connection with a potential reconfiguration of the existing fund complexes overseen by the boards of directors/trustees of the BlackRock-advised funds. The Fund has the same investment objectives, strategies and policies, portfolio management team and contractual arrangements, including the same contractual fees and expenses, as the Predecessor Fund. As a result, the performance of the Fund would have been substantially similar to that of the Predecessor Fund. The information shows you how the Predecessor Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The Predecessor Fund’s returns prior to October 1, 2011 as reflected in the bar chart and the table are the returns of a fund that followed different investment objectives and investment strategies under the name “BlackRock Government Income V.I. Fund.” The table compares the Predecessor Fund’s performance to that of the Bloomberg Barclays U.S. Government/Mortgage Index and the Bloomberg Barclays U.S. Mortgage-Backed Securities Index, which are relevant to the Fund because they have characteristics similar to the Fund’s investment strategies. The bar chart and table do not reflect separate account fees and expenses. If they did, returns would be less than those shown. The returns for Class III Shares prior to July 15, 2013, the recommencement of operations of the Class III Shares, are based upon performance of the Predecessor Fund’s Class I Shares, as adjusted to reflect the distribution and/or service (12b-1) fees applicable to Class III Shares. This information may be considered when assessing the performance of Class III Shares, but does not represent the actual performance of Class III Shares. To the extent that dividends and distributions have been paid by the Predecessor Fund, the performance information for the Predecessor Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance is not an indication of future results. If the Predecessor Fund’s investment manager and its affiliates had not waived or reimbursed certain Predecessor Fund expenses during these periods, the Predecessor Fund’s returns would have been lower.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The information shows you how the Predecessor Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund.
Performance Additional Market Index [Text]	rr_PerformanceAdditionalMarketIndex	The table compares the Predecessor Fund’s performance to that of the Bloomberg Barclays U.S. Government/Mortgage Index and the Bloomberg Barclays U.S. Mortgage-Backed Securities Index, which are relevant to the Fund because they have characteristics similar to the Fund’s investment strategies.
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	As with all such investments, past performance is not an indication of future results.
Bar Chart [Heading]	rr_BarChartHeading	Class I Shares ANNUAL TOTAL RETURNS BlackRock U.S. Government Bond V.I. Fund As of 12/31
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The bar chart and table do not reflect separate account fees and expenses. If they did, returns would be less than those shown.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the ten-year period shown in the bar chart, the highest return for a quarter was 7.73% (quarter ended December 31, 2008) and the lowest return for a quarter was -3.70% (quarter ended June 30, 2008).
Performance Table Heading	rr_PerformanceTableHeading	As of 12/31/17 Average Annual Total Returns
BlackRock U.S. Government Bond V.I. Fund | Class I Shares
Risk/Return:	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.50%	[1],[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Interest Expense	rr_Component1OtherExpensesOverAssets	0.14%
Miscellaneous Other Expenses	rr_Component2OtherExpensesOverAssets	0.67%
Other Expenses	rr_OtherExpensesOverAssets	0.81%	[3]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.31%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.20%)	[1],[4]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.11%	[1],[4]
1 Year	rr_ExpenseExampleYear01	$ 113
3 Years	rr_ExpenseExampleYear03	395
5 Years	rr_ExpenseExampleYear05	699
10 Years	rr_ExpenseExampleYear10	$ 1,562
2008	rr_AnnualReturn2008	7.69%
2009	rr_AnnualReturn2009	(1.64%)
2010	rr_AnnualReturn2010	8.67%
2011	rr_AnnualReturn2011	6.31%
2012	rr_AnnualReturn2012	2.41%
2013	rr_AnnualReturn2013	(3.25%)
2014	rr_AnnualReturn2014	5.87%
2015	rr_AnnualReturn2015	0.45%
2016	rr_AnnualReturn2016	1.33%
2017	rr_AnnualReturn2017	1.52%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	7.73%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.70%)
1 Year	rr_AverageAnnualReturnYear01	1.52%
5 Years	rr_AverageAnnualReturnYear05	1.14%
10 Years	rr_AverageAnnualReturnYear10	2.86%
BlackRock U.S. Government Bond V.I. Fund | Class III Shares
Risk/Return:	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.50%	[1],[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Interest Expense	rr_Component1OtherExpensesOverAssets	0.14%
Miscellaneous Other Expenses	rr_Component2OtherExpensesOverAssets	0.56%
Other Expenses	rr_OtherExpensesOverAssets	0.70%	[3]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.45%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[1],[4]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.40%	[1],[4]
1 Year	rr_ExpenseExampleYear01	$ 143
3 Years	rr_ExpenseExampleYear03	454
5 Years	rr_ExpenseExampleYear05	787
10 Years	rr_ExpenseExampleYear10	$ 1,731
1 Year	rr_AverageAnnualReturnYear01	1.10%
5 Years	rr_AverageAnnualReturnYear05	0.85%
10 Years	rr_AverageAnnualReturnYear10	2.59%
BlackRock U.S. Government Bond V.I. Fund | Bloomberg Barclays U.S. Government/Mortgage Index (Reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	2.37%
5 Years	rr_AverageAnnualReturnYear05	1.59%
10 Years	rr_AverageAnnualReturnYear10	3.51%
BlackRock U.S. Government Bond V.I. Fund | Bloomberg Barclays U.S. Mortgage-Backed Securities Index (Reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	2.47%
5 Years	rr_AverageAnnualReturnYear05	2.04%
10 Years	rr_AverageAnnualReturnYear10	3.84%

[1] As described in the “Management of the Funds” section of the Fund’s prospectus, BlackRock Advisors, LLC (“BlackRock”) has contractually agreed to waive the management fee with respect to any portion of the Fund’s assets estimated to be attributable to investments in other equity and fixed-income mutual funds and exchange-traded funds managed by BlackRock or its affiliates that have a contractual management fee, through April 30, 2020. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested directors of BlackRock Variable Series Funds II, Inc. (the “Company”) or by a vote of a majority of the outstanding voting securities of the Fund.

[2] Management Fee is based on the management fee rate of the Predecessor Fund (defined below).

[3] Other Expenses are based on estimated amounts for the current fiscal year, which are based on the expenses of the Predecessor Fund for its most recent fiscal year.

[4] As described in the “Management of the Funds” section of the Fund’s prospectus, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 1.25% (for Class I Shares) and 1.50% (for Class III Shares) of average daily net assets through April 30, 2020. BlackRock has also contractually agreed to reimburse fees in order to limit certain operational and recordkeeping fees to 0% (for Class I Shares) and 0.06% (for Class III Shares) of average daily net assets through April 30, 2020. Each of these contractual agreements may be terminated upon 90 days’ notice by a majority of the non-interested directors of the Company or by a vote of a majority of the outstanding voting securities of the Fund.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	BlackRock Variable Series Funds II, Inc.
Prospectus Date	rr_ProspectusDate	Jul. 02, 2018
Document Creation Date	dei_DocumentCreationDate	Jul. 02, 2018