Related Parties (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($) interest trustee	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Related Party Transaction [Line Items]
SMR trust ownership in NAI	80.00%
National Amusements Inc [Member]
Related Party Transaction [Line Items]
NAI ownership of CBS Corp. Class A common stock (percentage)	79.50%
NAI ownership of CBS Corp. Class A and Class B common stock on a combined basis (percentage)	10.20%
Number of trustees \| trustee	7
Viacom Inc [Member]
Related Party Transaction [Line Items]
Revenues from transactions with related parties	$ 145	$ 120	$ 176
Expenses from transactions with related parties	21	24	25
Amounts due from Related Party
Receivables	93	113
Other assets (Receivables, noncurrent)	11	35
Amounts due from related party	104	148
Equity Method Investees [Member]
Related Party Transaction [Line Items]
Revenues from transactions with related parties	99	112	$ 160
Amounts due from Related Party
Amounts due from related party	$ 27	$ 47
Number of equity interests \| interest	2

Chairman Emeritus trust ownership percentage in controlling stockholder

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Number of Equity Interests

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Number of Trustees

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Percent of CBS Corp. Class A and Class B Common Stock, on a combined basis, owned by NAI as of the financial statement date

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Percent of CBS Corp. Class A Common Stock owned by NAI as of the financial statement date

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For an unclassified balance sheet, amounts due from related parties including affiliates, employees, joint ventures, officers and stockholders, immediate families thereof, and pension funds.

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The aggregate amount of receivables to be collected from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth, at the financial statement date. which are usually due within one year (or one business cycle).

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Aggregate amount of receivables to be collected from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth, at the financial statement date. which are usually due after one year (or one business cycle).

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Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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