Stock Compensation - Intrinsic Value of Awards Exercised or Vested (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock Option And Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of awards exercised	$ 1	$ 7	$ 14
Restricted Stock Units (RSUs) and Performance Share Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of awards vested	$ 16	$ 8	$ 5

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.

No definition available.

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