Stock-Based Compensation (Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock Based Compensation Expense Details [Line Items]
Stock-based compensation expense, before income taxes	$ 165	$ 157	$ 137
Continuing Operations [Member]
Stock Based Compensation Expense Details [Line Items]
RSUs and PSUs	137	129	116
Stock options	28	28	21
Stock-based compensation expense, before income taxes	165	157	137
Related tax benefit	(63)	(61)	(55)
Stock-based compensation expense, net of tax benefit	102	96	82
Discontinued Operations [Member]
Stock Based Compensation Expense Details [Line Items]
Stock-based compensation expense, net of tax benefit	$ 12	$ 17	$ 17