Income Taxes (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Estimated annual effective tax rate (as a percent)	25.00%	28.00%	25.50%
Deferred Tax Assets, State, Net	$ 230
US Federal Statutory Income Tax Rate, Percent	35.00%
Prior year tax adjustment expense (benefit)			$ 42
Tax Year Prior Years
Income Tax Contingency
Income tax examination, proposed liability increase/(decrease)	$ 1,000
Income tax adjustment	$ 125