Income Taxes (Uncertain Tax Benefits) (Details 4) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Uncertain tax benefits
Liability for Uncertainty in Income Taxes, Noncurrent	$ 37	$ 35
Unrecognized Tax Benefits, Income Tax Penalties Expense	1
Accrued interest and penalties related to unrecognized tax benefits	4	3
Uncertain tax benefits reconciliation
Balance as of January 1	32	71
Increase due to current year positions	8	4
Decrease due to prior year positions	0	(25)
Unrecognized Tax Benefits, Increase Resulting from Acquisition	(6)	(18)
Uncertain tax benefits as of December 31	$ 34	$ 32