NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	Nature of Operations Sinclair Broadcast Group, Inc. is a diversified television broadcasting company with national reach with a strong focus on providing high-quality content on our local television stations and digital platforms. The content, distributed through our broadcast platform, consists of programming provided by third-party networks and syndicators, local news, and other original programming produced by us. We also distribute our original programming, and owned and operated network affiliates, on other third-party platforms. Additionally, we own digital media products that are complementary to our extensive portfolio of television station related digital properties. We focus on offering marketing solutions to advertisers through our television and digital platforms and digital agency services. Outside of our media related businesses, we operate technical services companies focused on supply and maintenance of broadcast transmission systems as well as research and development for the advancement of broadcast technology, and we manage other non-media related investments. As of December 31, 2017, our broadcast distribution platform is a single reportable segment for accounting purposes. It consists primarily of our broadcast television stations, which we own, provide programming and operating services pursuant to agreements commonly referred to as local marketing agreements (LMAs), or provide sales services and other non-programming operating services pursuant to other outsourcing agreements (such as joint sales agreements (JSAs) and shared services agreements (SSAs)) to 191 stations in 89 markets. These stations broadcast 601 channels as of December 31, 2017. For the purpose of this report, these 191 stations and 601 channels are referred to as “our” stations and channels.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include our accounts and those of our wholly-owned and majority-owned subsidiaries and variable interest entities (VIEs) for which we are the primary beneficiary. Noncontrolling interest represents a minority owner’s proportionate share of the equity in certain of our consolidated entities. All intercompany transactions and account balances have been eliminated in consolidation.
Variable Interest Entities	Other investments. We have several investments which are considered VIEs. However, we do not participate in the management of these entities including the day-to-day operating decisions or other decisions which would allow us to control the entity, and therefore, we are not considered the primary beneficiary of these VIEs. We account for these entities using the equity or cost method of accounting. Variable Interest Entities In determining whether we are the primary beneficiary of a VIE for financial reporting purposes, we consider whether we have the power to direct the activities of the VIE that most significantly impact the economic performance of the VIE and whether we have the obligation to absorb losses or the right to receive returns that would be significant to the VIE. We consolidate VIEs when we are the primary beneficiary. Third-party station licensees. Certain of our stations provide services to other station owners within the same respective market through agreements, such as LMAs, where we provide programming, sales, operational, and administrative services, and JSAs and SSAs, where we provide non-programming, sales, operational, and administrative services. In certain cases, we have also entered into purchase agreements or options to purchase the license related assets of the licensee. We typically own the majority of the non-license assets of the stations, and in some cases where the licensee acquired the license assets concurrent with our acquisition of the non-license assets of the station, we have provided guarantees to the bank for the licensee’s acquisition financing. The terms of the agreements vary, but generally have initial terms of over five years with several optional renewal terms. Based on the terms of the agreements and the significance of our investment in the stations, we are the primary beneficiary when, subject to the ultimate control of the licensees, we have the power to direct the activities which significantly impact the economic performance of the VIE through the services we provide and we absorb losses and returns that would be considered significant to the VIEs. The fees paid between us and the licensees pursuant to these arrangements are eliminated in consolidation. Several of these VIEs are owned by a related party, Cunningham Broadcasting Corporation (Cunningham).
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, and expenses in the consolidated financial statements and in the disclosures of contingent assets and liabilities. Actual results could differ from those estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued guidance on revenue recognition for revenue from contracts with customers. This guidance requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers and will replace most existing revenue recognition guidance when it becomes effective. The standard permits the use of either the retrospective or cumulative effect transition method. Since Accounting Standards Update (ASU) 2014-09 was issued, several additional ASUs have been issued and incorporated within ASC 606 to clarify various elements of the guidance. The adoption of this guidance will not have a material impact on our station advertising or retransmission consent revenue. We have determined that, under the new standard, certain barter revenue and expense related to syndicated programming will no longer be recognized. These revenues and expenses for the years ended December 31, 2017, 2016, and 2015 were each $97.9 million, $114.4 million, and $93.2 million, respectfully. The adoption of this standard will also result in a number of incremental disclosures surrounding our revenue transactions and policies. We plan on adopting this guidance retrospectively during the first quarter of 2018. In January 2016, the FASB issued new guidance which address certain aspects of recognition, measurement, presentation, and disclose of financial instruments. The new guidance requires entities to measure equity investments (except those accounted for under the equity method of accounting or those that resulted in consolidation of the investee) at fair value, with changes in fair value recognized in net income. The new standard is effective for the interim and annual periods beginning after December 15, 2017. We plan on adopting this guidance during the first quarter of 2018. We do not expect the adoption will have a material impact on our financial statements. In February 2016, the FASB issued new guidance related to accounting for leases, which requires the assets and liabilities that arise from leases to be recognized on the balance sheet. Currently, only capital leases are recorded on the balance sheet. This update will require the lessee to recognize a lease liability equal to the present value of the lease payments and a right-of-use asset representing its right to use the underlying asset for the lease term for all leases longer than 12 months. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election, by class of underlying asset, not to recognize lease assets and liabilities and recognize the lease expense for such leases generally on a straight-line basis over the lease term. The new standard is effective for interim and annual reporting periods beginning after December 15, 2018. Early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements. In August 2016, the FASB issued new guidance related to the classification of certain cash receipts and cash payments. The new standard includes eight specific cash flow issues with the objective of reducing the existing diversity in practice as to how cash receipts and cash payments are represented in the statement of cash flows. We will adopt this guidance retrospectively during the first quarter of 2018. In October 2016, the FASB issued new guidance related to the accounting for income tax consequences of intra-entity transfers of assets other than inventory. Currently the recognition of current and deferred income taxes for an intra-entity are prohibited until the asset has been sold to an outside party. This update requires an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. We adopted this guidance during the first quarter of 2017. The impact of the adoption did not have a material impact on our financial statements. In November 2016, the FASB issued new guidance related to the classification and presentation of changes in restricted cash on the statement of cash flows. This new guidance requires that the statement of cash flows explain change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. The new standard is effective for interim and annual reporting periods beginning after December 15, 2017. We plan on adopting this guidance retrospectively during the first quarter of 2018. In January 2017, the FASB issued guidance which clarifies the definition of a business with additional guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The new standard should be applied prospectively and is effective for interim and annual reporting periods beginning after December 15, 2017. We do not expect the adoption of this guidance to have a material impact on our financial statements. In January 2017, the FASB issued guidance which eliminates the requirement to calculate the implied fair value of goodwill to measure a goodwill impairment charge. The new standard should be applied prospectively and is effective for interim and annual reporting periods beginning after December 15, 2019. Early adoption is permitted. We adopted this guidance during the first quarter of 2017. The impact of the adoption did not have a material impact on our financial statements. In May 2017, the FASB issued new guidance which relates to stock based compensation and clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The new standard is effective for interim and annual reporting periods beginning after December 15, 2017. Early adoption is permitted. We adopted this guidance during the second quarter of 2017. The impact of the adoption did not have a material impact on our financial statements.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents.
Accounts Receivable	Accounts Receivable Management regularly reviews accounts receivable and determines an appropriate estimate for the allowance for doubtful accounts based upon the impact of economic conditions on the merchant’s ability to pay, past collection experience, and such other factors which, in management’s judgment, deserve current recognition. In turn, a provision is charged against earnings in order to maintain the appropriate allowance level.
Programming	Programming We have agreements with distributors for the rights to television programming over contract periods, which generally run from one to seven years. Contract payments are made in installments over terms that are generally equal to or shorter than the contract period. Pursuant to accounting guidance for the broadcasting industry, an asset and a liability for the rights acquired and obligations incurred under a license agreement are reported on the balance sheet where the cost of each program is known or reasonably determinable, the program material has been accepted by the licensee in accordance with the conditions of the license agreement, and the program is available for its first showing or telecast. The portion of program contracts which becomes payable within one year is reflected as a current liability in the accompanying consolidated balance sheets. The rights to this programming are reflected in the accompanying consolidated balance sheets at the lower of unamortized cost or estimated net realizable value. With the exception of one and two-year contracts, amortization of program contract costs is computed using an accelerated method. Program contract costs are amortized on a straight-line basis for one and two-year contracts. Program contract costs estimated by management to be amortized in the succeeding year are classified as current assets. Payments of program contract liabilities are typically made on a scheduled basis and are not affected by adjustments for amortization or estimated net realizable value. Estimated net realizable values are based on management’s expectation of future advertising revenues, net of sales commissions, to be generated by the program material. We perform a net realizable value calculation quarterly for each of our program contract costs in accordance with the accounting guidance for the broadcasting industry. We utilize sales information to estimate the future revenue of each commitment and measure that amount against the commitment. If the estimated future revenue is less than the amount of the commitment, a loss is recorded in amortization of program contract costs and net realizable value adjustments in the consolidated statements of operations.
Barter Arrangements	Barter Arrangements Certain program contracts provide for the exchange of advertising airtime in lieu of cash payments for the rights to such programming. The revenues realized from station barter arrangements are recorded as the programs are aired at the estimated fair value of the advertising airtime given in exchange for the program rights. Program service arrangements are accounted for as station barter arrangements, however, network affiliation programming is excluded from these calculations. Revenues are recorded as revenues realized from station barter arrangements and the corresponding expenses are recorded as expenses recognized from station barter arrangements. See Recent Accounting Pronouncements above for more information about guidance that will be adopted effective January 1, 2018. We broadcast certain customers’ advertising in exchange for equipment, merchandise and services. The estimated fair value of the equipment, merchandise, or services received is recorded as deferred barter costs, included in prepaid expenses and other current assets in the consolidated balance sheets, and the corresponding obligation to broadcast advertising is recorded as deferred barter revenues, included in accounts payable and accrued liabilities in the consolidated balance sheets. The deferred barter costs are expensed or capitalized as they are used, consumed, or received and are included in station production expenses and station selling, general and administrative expenses, as applicable. Deferred barter revenues are recognized as the related advertising is aired and are recorded in revenues realized from station barter arrangements.
Other Assets	We have equity and cost method investments primarily in private equity investments and real estate ventures. In the event one or more of our investments are significant, we are required to disclose summarized financial information. For the years ended December 31, 2017, 2016, and 2015, none of our investments were significant individually or in the aggregate. As of December 31, 2017 and 2016, our unfunded commitments related to certain investments accounted for under the equity or cost method totaled $10.7 million and $13.5 million, respectively. When factors indicate that there may be a decrease in value of an equity or cost method investment, we assess whether a loss in value has occurred related to the investment. If that loss is deemed to be other than temporary, an impairment loss is recorded accordingly. For any investments that indicate a potential impairment, we estimate the fair values of those investments using discounted cash flow models, unrelated third party valuations, or industry comparables, based on the various facts available to us. For the year ended December 31, 2017, we recorded a $3.3 million impairment charge related to three real estate investments. For the year ended December 31, 2016, there were $2.5 million of impairment charges recorded. The impairments are recorded in the income (loss) from equity and cost method investments in our consolidated statement of operations. Unamortized costs related to debt issuances represent costs related to our revolving credit facility. Unamortized costs related to our other debt issuances is recorded as a direct deduction from the carrying value of the debt recorded as liability. We amortize our deferred debt financing costs to interest expense over the term of the respective debt instruments using the effective interest method. Previously capitalized debt financing costs are recognized as a loss on extinguishment of debt if we determine that there has been an extinguishment of the related debt.
Impairment of Goodwill, Intangibles and Other Long-Lived Assets	Impairment of Goodwill, Intangibles and Other Long-Lived Assets We evaluate our goodwill and indefinite lived intangible assets for impairment annually in the fourth quarter or more frequently, if events or changes in circumstances indicate that an impairment may exist. Our goodwill has been allocated to, and is tested for impairment at the reporting unit level. A reporting unit is an operating segment or a component of an operating segment to the extent that the component constitutes a business for which discrete financial information is available and regularly reviewed by segment management. Components of an operating segment with similar economic characteristics are aggregated when testing goodwill for impairment. In the performance of our annual assessment of goodwill for impairment we have the option to qualitatively assess whether it is more likely than not a reporting unit has been impaired. As part of this qualitative assessment we weigh the relative impact of factors that are specific to the reporting units as well as industry, regulatory, and macroeconomic factors that could affect the significant inputs used to determine the fair value of the assets. We also consider the significance of the excess fair value over carrying value in prior quantitative assessments. If we conclude that it is more likely than not that a reporting unit is impaired, or if we elect not to perform the optional qualitative assessment, we will determine the fair value of the reporting unit and compare to the net book value of the reporting unit. If the fair value is less than the net book value we will record an impairment to goodwill for the amount of the difference. We estimate the fair value of our reporting units utilizing a combination of a market based approach which considers earnings and cash flow multiples of comparable businesses and recent market transactions as well as an income approach involving the performance of a discounted cash flow analysis. Our discounted cash flow model is based on our judgment of future market conditions based on our internal forecast of future performance, as well as discount rates that are based on a number of factors including market interest rates, a weighted average cost of capital analysis, and includes adjustments for market risk and company specific risk. Our indefinite-lived intangible assets consist primarily of our broadcast licenses and a trade name. For our annual impairment test for indefinite-lived intangible assets we have the option to perform a qualitative assessment to determine whether it is more likely than not that these assets are impaired. As part of this qualitative assessment we weigh the relative impact of factors that are specific to the indefinite-lived intangible assets as well as industry, regulatory, and macroeconomic factors that could affect the significant inputs used to determine the fair value of the assets. We also consider the significance of the excess fair value over carrying value in prior quantitative assessments. When evaluating our broadcast licenses for impairment, the qualitative assessment is done at the market level because the broadcast licenses within the market are complementary and together enhance the single broadcast license of each station. If we conclude that it is more likely than not that one of our broadcast licenses is impaired, we will perform a quantitative assessment by comparing the aggregate fair value of the broadcast licenses in the market to the respective carrying values. We estimate the fair values of our broadcast licenses using the Greenfield method which is an income approach. This method involves a discounted cash flow model that incorporates several variables, including, but not limited to, market revenues and long term growth projections, estimated market share for the typical participant without a network affiliation, and estimated profit margins based on market size and station type. The model also assumes outlays for capital expenditures, future terminal values, an effective tax rate assumption and a discount rate based on a number of factors including market interest rates, a weighted average cost of capital analysis based on the target capital structure for a television station, and includes adjustments for market risk and company specific risk. If the carrying amount of the broadcast licenses exceeds the fair value, then an impairment loss is recorded to the extent that the carrying value of the broadcast licenses exceeds the fair value. We periodically evaluate our long-lived assets for impairment and continue to evaluate them as events or changes in circumstances indicate that the carrying amount of such assets may not be fully recoverable. We evaluate the recoverability of long-lived assets by measuring the carrying amount of the assets against the estimated undiscounted future cash flows associated with them. At the time that such evaluations indicate that the future undiscounted cash flows of certain long-lived assets are not sufficient to recover the carrying value of such assets, the assets are tested for impairment by comparing their estimated fair value to the carrying value. We typically estimate fair value using discounted cash flow models and appraisals.
Accrued Liabilities	We expense these activities when incurred.
Income Taxes	Income Taxes We recognize deferred tax assets and liabilities based on the differences between the financial statement carrying amounts and the tax bases of assets and liabilities. We provide a valuation allowance for deferred tax assets if we determine that it is more likely than not that some or all of the deferred tax assets will not be realized. In evaluating our ability to realize net deferred tax assets, we consider all available evidence, both positive and negative, including our past operating results, tax planning strategies and forecasts of future taxable income. In considering these sources of taxable income, we must make certain judgments that are based on the plans and estimates used to manage our underlying businesses on a long-term basis. As of December 31, 2017 and 2016, a valuation allowance has been provided for deferred tax assets related to a substantial amount of our available state net operating loss carryforwards based on past operating results, expected timing of the reversals of existing temporary book/tax basis differences, alternative tax strategies and projected future taxable income. Future changes in operating and/or taxable income or other changes in facts and circumstances could significantly impact the ability to realize our deferred tax assets which could have a material effect on our consolidated financial statements. Management periodically performs a comprehensive review of our tax positions and we record a liability for unrecognized tax benefits when such tax positions do not meet the “more-likely-than-not” threshold. Significant judgment is required in determining whether a tax position meets the “more-likely-than-not” threshold, and it is based on a variety of facts and circumstances, including interpretation of the relevant federal and state income tax codes, regulations, case law and other authoritative pronouncements. Based on this analysis, the status of ongoing audits and the expiration of applicable statute of limitations, liabilities are adjusted as necessary. The resolution of audits is unpredictable and could result in tax liabilities that are significantly higher or lower than for what we have provided. See Note 9. Income Taxes, for further discussion of accrued unrecognized tax benefits. Pursuant to the guidance within SEC Staff Accounting Bulletin No. 118 (SAB 118), as of December 31, 2017, the Company recognized the provisional effects of the enactment of the Tax Legislation for which measurement could be reasonably estimated. Although the Company continues to analyze certain aspects of the Tax Legislation and refine its assessment, the ultimate impact of the Tax Legislation may differ from these estimates due to its continued analysis or further regulatory guidance that may be issued as a result of the Tax Legislation. Pursuant to SAB 118, adjustments to the provisional amounts recorded by the Company as of December 31, 2017 that are identified within a subsequent measurement period of up to one year from the enactment date will be included as an adjustment to tax expense from continuing operations in the period the amounts are determined.
Revenue Recognition	Revenue Recognition Total revenues include: (i) station advertising revenue, net of agency commissions; (ii) barter advertising revenues; (iii) retransmission consent fees; (iv) other media revenues; and (v) revenues from our other businesses. Advertising revenues, net of agency commissions, are recognized in the period during which advertisements are placed. Some of our retransmission consent agreements contain both advertising and retransmission consent elements. We have determined that these retransmission consent agreements are revenue arrangements with multiple deliverables. Advertising and retransmission consent deliverables sold under our agreements are separated into different units of accounting at fair value. Revenue applicable to the advertising element of the arrangement is recognized similar to the advertising revenue policy noted above. Revenue applicable to the retransmission consent element of the arrangement is recognized over the life of the agreement.
Advertising Expenses	Advertising Expenses Promotional advertising expenses are recorded in the period when incurred and are included in media production and other non-media expenses.
Financial Instruments	Financial Instruments Financial instruments, as of December 31, 2017 and 2016, consisted of cash and cash equivalents, trade accounts receivable, accounts payable, accrued liabilities, and notes payable. The carrying amounts approximate fair value for each of these financial instruments, except for the notes payable.
Post-retirement Benefits	Post-retirement Benefits During the fourth quarter of 2015, we fully settled the benefit obligation of our pension plan. We relieved our benefit obligation via lump sum distributions and/or the purchase of annuity contracts. Upon settlement we recorded $9.3 million of pension expense, including the recognition of $8.0 million of unamortized actuarial losses which was recorded in accumulated other comprehensive income, and $4.6 million of pension liability, representing the underfunded status of our defined pension plan, which was included within other long-term liabilities within our consolidated balance sheet. We maintain a supplemental executive retirement plan (SERP) which we inherited upon the acquisition of certain stations. As of December 31, 2017, the estimated projected benefit obligation was $21.5 million, of which $1.7 million is included in accrued expenses in the consolidated balance sheet and the $19.8 million is included in other long-term liabilities. During the years ended December 31, 2017 and 2016, we made $1.8 million and $1.7 million in benefit payments, recognized $0.8 million and $0.9 million of periodic pension expense, reported in other expenses in the consolidated statement of operations, and $1.0 million and $0.1 million of actuarial gains through other comprehensive income, respectively. At December 31, 2017, the projected benefit obligation was measured using a 3.46% discount rate compared to a discount rate of 3.89% for the year ended December 31, 2016. We estimated the discount rate, in consultation with our independent actuaries, based on a yield curve constructed from a portfolio of high quality bonds for which the timing and amount of cash outflows approximate the estimated payouts of the plan.
Reclassifications	Reclassifications Certain reclassifications have been made to prior years’ consolidated financial statements to conform to the current year’s presentation.