Stock-Based Compensation Plans - Schedule of Stock-based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 119	$ 127	$ 118	[1]
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ (46)	$ (47)	$ (44)

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