Significant Accounting Policies	3 Months Ended
Mar. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Recently Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Codification (“ASC”) 606, Revenue from Contracts with Customers, which outlines a single comprehensive revenue recognition model for all contracts with customers and supersedes most of the existing revenue recognition requirements. We adopted this new standard on January 1, 2018 on a modified retrospective basis for contracts that were not completed as of the date of adoption. The new standard did not change the timing of revenue recognition for our base fees, distribution revenues, shareholder servicing fees and broker-dealer revenues. However, performance-based fees, which, prior to the adoption of ASC 606, were recognized at the end of the applicable measurement period when no risk of reversal remained, and carried-interest distributions received (considered performance-based fees), recorded as deferred revenues until no risk of reversal remained, may in certain instances be recognized earlier under the new standard, if it is probable that significant reversal of performance-based fees recognized will not occur. On January 1, 2018, we recorded a cumulative effect adjustment, net of tax, of a $35.0 million increase to partners’ capital in the condensed consolidated statement of financial condition. This amount represents carried-interest distributions of $77.9 million previously received, net of revenue sharing payments to investment team-members of $42.7 million, with respect to which it is probable that significant reversal will not occur. In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities. The amendment addresses certain aspects of recognition, measurement, presentation and disclosure of financial instruments. We adopted this standard on January 1, 2018. The adoption of this standard did not have a material impact on our financial condition or results of operations. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230). The amendment is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. We adopted this standard on January 1, 2018. The adoption of this standard did not have a material impact on our financial condition or results of operations. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash. The new standard requires that the statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Companies are also required to reconcile such total amounts in the balance sheet and disclose the nature of the restrictions. We adopted this standard on January 1, 2018. The adoption of this standard did not have a material impact on our financial condition or results of operations. In March 2017, the FASB issued ASU 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. The amendment requires that an employer disaggregate the service cost component from the other components of net benefit costs on the income statement. We adopted this standard on January 1, 2018. The adoption of this standard did not have a material impact on our financial condition or results of operations. In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation, Scope of Modification Accounting. The amendment provides clarity and reduces both diversity in practice and cost and complexity when applying the guidance in Topic 718, Compensation - Stock Compensation, to a change to the terms or conditions of a share-based payment award. We adopted this standard on January 1, 2018. The adoption of this standard did not have a material impact on our financial condition or results of operations. Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, Leases. The amendment requires recognition of lease assets and lease liabilities on the statement of financial condition and disclosure of key information about leasing arrangements. Specifically, this guidance requires an operating lease lessee to recognize on the statement of financial condition a liability to make lease payments and a right-of-use asset representing its right to use the underlying asset for the lease term. However, for leases with a term of twelve months or less, a lessee is permitted to make an accounting policy election not to recognize lease assets and lease liabilities. The amendment is effective for fiscal years (and interim periods within those years) beginning after December 15, 2018 and requires lessees to recognize and measure leases at the beginning of the earliest period presented in the financial statements using a modified retrospective approach. Management currently is evaluating the impact that the adoption of this standard will have on our consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment. The guidance removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. As a result of the revised guidance, a goodwill impairment will be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The revised guidance will be applied prospectively, and is effective in 2020. The revised guidance is not expected to have a material impact on our financial condition or results of operations. In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, which permits a company to reclassify the disproportionate income tax effects of the 2017 Tax Cuts and Job Act ("2017 Tax Act") on items within Accumulated Other Comprehensive Income ("AOCI") to retained earnings. The FASB refers to these amounts as "stranded tax effects." The ASU also requires certain new disclosures, some of which are applicable for all companies. The guidance is effective for all companies for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Companies may adopt the new guidance using one of two transition methods: (1) retrospective to each period (or periods) in which the income tax effect of the 2017 Tax Act related to items remaining in AOCI are recognized, or (2) at the beginning of the period of adoption. The adoption of this standard is not expected to have a material impact on our financial condition or results of operations. Revenue Recognition Investment advisory and services fees AB provides asset management services by managing customer assets and seeking to deliver investment returns to investors. Each investment management contract between AB and a customer creates a distinct, separately identifiable performance obligation for each day the customer’s assets are managed as the customer can benefit from each day of service. In accordance with ASC 606, a series of distinct goods and services that are substantially the same and have the same pattern of transfer to the customer are treated as a single performance obligation. Accordingly, we have determined that our investment and advisory services are performed over time and entitle us to variable consideration earned based upon the value of the investors’ assets under management (“AUM”). We calculate AUM using established market-based valuation methods and fair valuation (non-observable market) methods. Market-based valuation methods include: last sale/settle prices from an exchange for actively-traded listed equities, options and futures; evaluated bid prices from recognized pricing vendors for fixed income, asset-backed or mortgage-backed issues; mid prices from recognized pricing vendors and brokers for credit default swaps; and quoted bids or spreads from pricing vendors and brokers for other derivative products. Fair valuation methods include: discounted cash flow models, evaluation of assets versus liabilities or any other methodology that is validated and approved by our Valuation Committee (see paragraph immediately below for additional information about our Valuation Committee). Fair valuation methods are used only where AUM cannot be valued using market-based valuation methods, such as in the case of private equity or illiquid securities. The Valuation Committee, which consists of senior officers and employees, is responsible for overseeing the pricing and valuation of all investments held in client and AB portfolios. The Valuation Committee has adopted a Statement of Pricing Policies describing principles and policies that apply to pricing and valuing investments held in these portfolios. We also have a Pricing Group, which reports to the Valuation Committee, and is responsible for overseeing the pricing process for all investments. We record as revenue investment advisory and services base fees, which we generally calculate as a percentage of AUM. At month-end, all the components of the transaction price (i.e. the base fee calculation) are no longer variable and the value of the consideration is determined. These fees are not subject to claw back and there is minimal probability that a significant reversal of the revenue recorded will occur. The transaction price for the asset management performance obligation for certain investment advisory contracts, including those associated with hedge funds or other alternative investments, provide for a performance-based fee (including carried interest), in addition to a base advisory fee, which is calculated as either a percentage of absolute investment results or a percentage of investment results in-excess-of a stated benchmark over a specified period-of-time. The performance-based fees are forms of variable consideration and are therefore excluded from the transaction price until it becomes probable that there will not be significant reversal of the cumulative revenue recognized. At each reporting date, we evaluate the constraining factors, discussed below, surrounding the variable consideration to determine the extent to which, if any, that revenues associated with the performance-based fee can be recognized. Constraining factors impacting the amount of variable consideration included in the transaction price include: the contractual claw-back provisions the variable consideration is subject to, the length of time the uncertainty of the consideration is subject to, the number and range of possible consideration amounts, the probability of significant fluctuations in the fund’s market value, the level at which the fund’s value exceeds the contractual threshold required to earn such a fee and the materiality of the amount being evaluated. Prior to the adoption of ASC 606 on January 1, 2018, we recognized performance-based fees at the end of the applicable measurement period when no risk of reversal remained, and carried-interest distributions received as deferred revenues until no risk of reversal remained. Bernstein Research Services Bernstein Research Services revenue consists principally of commissions received for trade execution services and providing equity research services to institutional clients. Brokerage commissions for trade execution services and related expenses are recorded on a trade-date basis when the performance obligations are satisfied. Generally, the transaction price is agreed upon at the point of each trade and based upon the number of shares traded or the value of the consideration traded. Research revenues are recognized when the transaction price is quantified, collectability is assured and that significant reversal of such revenue is not probable. Distribution Revenues Two of our subsidiaries act as distributors and/or placement agents of company-sponsored mutual funds and receive distribution services fees from certain of those funds as partial reimbursement of the distribution expenses they incur. Depending upon the contractual arrangements with the customer and the specific product sold, the variable consideration can be determined in different ways, as discussed below, as we satisfy the performance obligation. Most open-end U.S. funds have adopted a plan under Rule 12b-1 of the Investment Company Act that allows the fund to pay, out of assets of the fund, distribution and service fees for the distribution and sale of its shares (“Rule 12b-1 Fees”). The open-end U.S. funds have such agreements with us, and we have selling and distribution agreements pursuant to which we pay sales commissions to the financial intermediaries that distribute our open-end U.S. funds. These agreements are terminable by either party upon notice (generally 30 days) and do not obligate the financial intermediary to sell any specific amount of fund shares. We record 12b-1 fees monthly based upon a percentage of the net asset value (“NAV”) of the funds. At month-end, the variable consideration of the transaction price is no longer constrained as the NAV can be calculated and the value of consideration is determined. These services are separate and distinct from other asset management services as the customer can benefit from these services independently of other services. We accrue the corresponding 12b-1 fees paid to sub-distributors monthly as the expenses are incurred. We are acting in a principal capacity in these transactions; as such, these revenues and expenses are recorded on a gross basis. We offer back-end load shares in limited instances and charge the investor a contingent deferred sales charge (“CDSC”) if the investment is redeemed within a certain period. The variable consideration for these contracts is contingent upon the timing of the redemption by the investor and the value of the sale proceeds. Due to these constraining factors, we exclude the CDSC fee from the transaction price until the investor redeems the investment. Upon redemption, the cash consideration received for these contractual arrangements are recorded as reductions of unamortized deferred sales commissions. Our Luxembourg subsidiary, the management company for most of our non-U.S. funds, earns a management fee which is accrued daily and paid monthly, at an annual rate, based on the average daily net assets of the fund. With respect to certain share classes, the management fee may also contain a component that is paid to distributors and other financial intermediaries and service providers to cover shareholder servicing and other administrative expenses (also referred to as an All-in-Fee). As we have concluded that asset management is distinct from distribution, we allocate a portion of the investment and advisory fee to distribution revenues for the servicing component based on standalone selling prices. Other Revenues Revenues from contracts with customers include a portion of other revenues, which consists primarily of shareholder servicing fees, as well as mutual fund reimbursements and other brokerage income. We provide shareholder services, which include transfer agency, administrative and recordkeeping services provided to company-sponsored mutual funds. The consideration for these services is based on a percentage of the NAV of the fund or a fixed-fee based on the number of shareholder accounts being serviced. The revenues are recorded at month-end when the constraining factors involved with determining NAV or the number of shareholders’ accounts are resolved. Non-Contractual Revenues Dividend and interest income is accrued as earned. Investment gains and losses on the condensed consolidated statements of income include unrealized gains and losses of trading and private equity investments stated at fair value, equity in earnings of our limited partnership hedge fund investments, and realized gains and losses on investments sold. Contract Assets and Liabilities We use the practical expedient for contracts that have an original duration of one year or less. Accordingly, we do not consider the time value of money and, instead, accrue the incremental costs of obtaining the contract when incurred. As of March 31, 2018, the balances of contract assets and contract liabilities are not considered material and, accordingly, no further disclosures are necessary.

Significant Accounting Policies

Recently Adopted Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Codification (“ASC”) 606, Revenue from Contracts with Customers, which outlines a single comprehensive revenue recognition model for all contracts with customers and supersedes most of the existing revenue recognition requirements. We adopted this new standard on January 1, 2018 on a modified retrospective basis for contracts that were not completed as of the date of adoption.

The new standard did not change the timing of revenue recognition for our base fees, distribution revenues, shareholder servicing fees and broker-dealer revenues. However, performance-based fees, which, prior to the adoption of ASC 606, were recognized at the end of the applicable measurement period when no risk of reversal remained, and carried-interest distributions received (considered performance-based fees), recorded as deferred revenues until no risk of reversal remained, may in certain instances be recognized earlier under the new standard, if it is probable that significant reversal of performance-based fees recognized will not occur.

On January 1, 2018, we recorded a cumulative effect adjustment, net of tax, of a $35.0 million increase to partners’ capital in the condensed consolidated statement of financial condition. This amount represents carried-interest distributions of $77.9 million previously received, net of revenue sharing payments to investment team-members of $42.7 million, with respect to which it is probable that significant reversal will not occur.

In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities. The amendment addresses certain aspects of recognition, measurement, presentation and disclosure of financial instruments. We adopted this standard on January 1, 2018. The adoption of this standard did not have a material impact on our financial condition or results of operations.

In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230). The amendment is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. We adopted this standard on January 1, 2018. The adoption of this standard did not have a material impact on our financial condition or results of operations.

In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash. The new standard requires that the statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Companies are also required to reconcile such total amounts in the balance sheet and disclose the nature of the restrictions. We adopted this standard on January 1, 2018. The adoption of this standard did not have a material impact on our financial condition or results of operations.

In March 2017, the FASB issued ASU 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. The amendment requires that an employer disaggregate the service cost component from the other components of net benefit costs on the income statement. We adopted this standard on January 1, 2018. The adoption of this standard did not have a material impact on our financial condition or results of operations.

In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation, Scope of Modification Accounting. The amendment provides clarity and reduces both diversity in practice and cost and complexity when applying the guidance in Topic 718, Compensation - Stock Compensation, to a change to the terms or conditions of a share-based payment award. We adopted this standard on January 1, 2018. The adoption of this standard did not have a material impact on our financial condition or results of operations.

Accounting Pronouncements Not Yet Adopted

In February 2016, the FASB issued ASU 2016-02, Leases. The amendment requires recognition of lease assets and lease liabilities on the statement of financial condition and disclosure of key information about leasing arrangements. Specifically, this guidance requires an operating lease lessee to recognize on the statement of financial condition a liability to make lease payments and a right-of-use asset representing its right to use the underlying asset for the lease term. However, for leases with a term of twelve months or less, a lessee is permitted to make an accounting policy election not to recognize lease assets and lease liabilities. The amendment is effective for fiscal years (and interim periods within those years) beginning after December 15, 2018 and requires lessees to recognize and measure leases at the beginning of the earliest period presented in the financial statements using a modified retrospective approach. Management currently is evaluating the impact that the adoption of this standard will have on our consolidated financial statements.

In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment. The guidance removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. As a result of the revised guidance, a goodwill impairment will be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The revised guidance will be applied prospectively, and is effective in 2020. The revised guidance is not expected to have a material impact on our financial condition or results of operations.

In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, which permits a company to reclassify the disproportionate income tax effects of the 2017 Tax Cuts and Job Act ("2017 Tax Act") on items within Accumulated Other Comprehensive Income ("AOCI") to retained earnings. The FASB refers to these amounts as "stranded tax effects." The ASU also requires certain new disclosures, some of which are applicable for all companies. The guidance is effective for all companies for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Companies may adopt the new guidance using one of two transition methods: (1) retrospective to each period (or periods) in which the income tax effect of the 2017 Tax Act related to items remaining in AOCI are recognized, or (2) at the beginning of the period of adoption. The adoption of this standard is not expected to have a material impact on our financial condition or results of operations.

Revenue Recognition

Investment advisory and services fees

AB provides asset management services by managing customer assets and seeking to deliver investment returns to investors. Each investment management contract between AB and a customer creates a distinct, separately identifiable performance obligation for each day the customer’s assets are managed as the customer can benefit from each day of service. In accordance with ASC 606, a series of distinct goods and services that are substantially the same and have the same pattern of transfer to the customer are treated as a single performance obligation. Accordingly, we have determined that our investment and advisory services are performed over time and entitle us to variable consideration earned based upon the value of the investors’ assets under management (“AUM”).

We calculate AUM using established market-based valuation methods and fair valuation (non-observable market) methods. Market-based valuation methods include: last sale/settle prices from an exchange for actively-traded listed equities, options and futures; evaluated bid prices from recognized pricing vendors for fixed income, asset-backed or mortgage-backed issues; mid prices from recognized pricing vendors and brokers for credit default swaps; and quoted bids or spreads from pricing vendors and brokers for other derivative products. Fair valuation methods include: discounted cash flow models, evaluation of assets versus liabilities or any other methodology that is validated and approved by our Valuation Committee (see paragraph immediately below for additional information about our Valuation Committee). Fair valuation methods are used only where AUM cannot be valued using market-based valuation methods, such as in the case of private equity or illiquid securities.

The Valuation Committee, which consists of senior officers and employees, is responsible for overseeing the pricing and valuation of all investments held in client and AB portfolios. The Valuation Committee has adopted a Statement of Pricing Policies describing principles and policies that apply to pricing and valuing investments held in these portfolios. We also have a Pricing Group, which reports to the Valuation Committee, and is responsible for overseeing the pricing process for all investments.

We record as revenue investment advisory and services base fees, which we generally calculate as a percentage of AUM. At month-end, all the components of the transaction price (i.e. the base fee calculation) are no longer variable and the value of the consideration is determined. These fees are not subject to claw back and there is minimal probability that a significant reversal of the revenue recorded will occur.

The transaction price for the asset management performance obligation for certain investment advisory contracts, including those associated with hedge funds or other alternative investments, provide for a performance-based fee (including carried interest), in addition to a base advisory fee, which is calculated as either a percentage of absolute investment results or a percentage of investment results in-excess-of a stated benchmark over a specified period-of-time. The performance-based fees are forms of variable consideration and are therefore excluded from the transaction price until it becomes probable that there will not be significant reversal of the cumulative revenue recognized. At each reporting date, we evaluate the constraining factors, discussed below, surrounding the variable consideration to determine the extent to which, if any, that revenues associated with the performance-based fee can be recognized.

Constraining factors impacting the amount of variable consideration included in the transaction price include: the contractual claw-back provisions the variable consideration is subject to, the length of time the uncertainty of the consideration is subject to, the number and range of possible consideration amounts, the probability of significant fluctuations in the fund’s market value, the level at which the fund’s value exceeds the contractual threshold required to earn such a fee and the materiality of the amount being evaluated.

Prior to the adoption of ASC 606 on January 1, 2018, we recognized performance-based fees at the end of the applicable measurement period when no risk of reversal remained, and carried-interest distributions received as deferred revenues until no risk of reversal remained.

Bernstein Research Services

Bernstein Research Services revenue consists principally of commissions received for trade execution services and providing equity research services to institutional clients. Brokerage commissions for trade execution services and related expenses are recorded on a trade-date basis when the performance obligations are satisfied. Generally, the transaction price is agreed upon at the point of each trade and based upon the number of shares traded or the value of the consideration traded. Research revenues are recognized when the transaction price is quantified, collectability is assured and that significant reversal of such revenue is not probable.

Distribution Revenues

Two of our subsidiaries act as distributors and/or placement agents of company-sponsored mutual funds and receive distribution services fees from certain of those funds as partial reimbursement of the distribution expenses they incur. Depending upon the contractual arrangements with the customer and the specific product sold, the variable consideration can be determined in different ways, as discussed below, as we satisfy the performance obligation.

Most open-end U.S. funds have adopted a plan under Rule 12b-1 of the Investment Company Act that allows the fund to pay, out of assets of the fund, distribution and service fees for the distribution and sale of its shares (“Rule 12b-1 Fees”). The open-end U.S. funds have such agreements with us, and we have selling and distribution agreements pursuant to which we pay sales commissions to the financial intermediaries that distribute our open-end U.S. funds. These agreements are terminable by either party upon notice (generally 30 days) and do not obligate the financial intermediary to sell any specific amount of fund shares.

We record 12b-1 fees monthly based upon a percentage of the net asset value (“NAV”) of the funds. At month-end, the variable consideration of the transaction price is no longer constrained as the NAV can be calculated and the value of consideration is determined. These services are separate and distinct from other asset management services as the customer can benefit from these services independently of other services. We accrue the corresponding 12b-1 fees paid to sub-distributors monthly as the expenses are incurred. We are acting in a principal capacity in these transactions; as such, these revenues and expenses are recorded on a gross basis.

We offer back-end load shares in limited instances and charge the investor a contingent deferred sales charge (“CDSC”) if the investment is redeemed within a certain period. The variable consideration for these contracts is contingent upon the timing of the redemption by the investor and the value of the sale proceeds. Due to these constraining factors, we exclude the CDSC fee from the transaction price until the investor redeems the investment. Upon redemption, the cash consideration received for these contractual arrangements are recorded as reductions of unamortized deferred sales commissions.

Our Luxembourg subsidiary, the management company for most of our non-U.S. funds, earns a management fee which is accrued daily and paid monthly, at an annual rate, based on the average daily net assets of the fund. With respect to certain share classes, the management fee may also contain a component that is paid to distributors and other financial intermediaries and service providers to cover shareholder servicing and other administrative expenses (also referred to as an All-in-Fee). As we have concluded that asset management is distinct from distribution, we allocate a portion of the investment and advisory fee to distribution revenues for the servicing component based on standalone selling prices.

Other Revenues

Revenues from contracts with customers include a portion of other revenues, which consists primarily of shareholder servicing fees, as well as mutual fund reimbursements and other brokerage income.

We provide shareholder services, which include transfer agency, administrative and recordkeeping services provided to company-sponsored mutual funds. The consideration for these services is based on a percentage of the NAV of the fund or a fixed-fee based on the number of shareholder accounts being serviced. The revenues are recorded at month-end when the constraining factors involved with determining NAV or the number of shareholders’ accounts are resolved.

Non-Contractual Revenues

Dividend and interest income is accrued as earned. Investment gains and losses on the condensed consolidated statements of income include unrealized gains and losses of trading and private equity investments stated at fair value, equity in earnings of our limited partnership hedge fund investments, and realized gains and losses on investments sold.

Contract Assets and Liabilities

We use the practical expedient for contracts that have an original duration of one year or less. Accordingly, we do not consider the time value of money and, instead, accrue the incremental costs of obtaining the contract when incurred. As of March 31, 2018, the balances of contract assets and contract liabilities are not considered material and, accordingly, no further disclosures are necessary.