Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Beginning balance	$ 49	$ 72
Additions related to current years' tax positions	1	1
Additions related to prior years' tax positions	16	17
Unrecognized Tax Benefits, Increase Resulting from Acquisition	0	7
Reductions related to prior years' tax positions	0	(19)
Reductions due to lapse of statue of limitations	(1)	(6)
Settlements with tax authorities	(10)	(23)
Ending balance	$ 55	$ 49