Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal	$ (30)	$ 0	$ (10)
State	2	6	6
Puerto Rico	17	38	10
Total current tax expense (benefit)	(11)	44	6
Federal	281	79	24
State	(37)	40	(22)
Puerto Rico	12	3	8
Total deferred tax expense	256	122	10
Total income tax expense	$ 245	$ 166	$ 16