Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Beginning balance	$ 72	$ 66
Additions related to current years' tax positions	1	5
Additions related to prior years' tax positions	17	7
Unrecognized Tax Benefits, Increase Resulting from Acquisition	7	0
Reductions related to prior years' tax positions	(19)	(3)
Reductions due to lapse of statue of limitations	(6)	0
Settlements with tax authorities	(23)	(3)
Ending balance	$ 49	$ 72