Income Taxes (details) - Additional Tax Details - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of unrecognized tax benefits [Roll Forward]
Unrecognized tax benefits, balance at January 1	$ 23	$ 21
Additions for tax positions of prior years	2	2
Reductions for tax positions of prior years	(9)
Unrecognized tax benefits, balance at December 31	16	23	$ 21
Unrecognized tax benefits that, if recognized, would affect the annual effective tax rate	4	2
Amount of unrecognized tax benefits that are tax positions for which the ultimate deductibility is certain, but for which there is uncertainty about the timing of deductibility	12	21
Amount of interest recognized on unrecognized tax benefits in income taxes		31
Amount of interest benefit recognized on unrecognized tax benefits in income taxes	(32)		$ (67)
Accrued payment of interest balance for unrecognized tax benefits	$ 26	$ 58