Income Taxes Income Taxes (Schedule of Significant Components of Income Tax Expense) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Current Federal Tax Expense (Benefit)									$ 0	$ 0	$ (3)
Current Foreign Tax Expense (Benefit)									8	6	8
Current State and Local Tax Expense (Benefit)									9	3	5
Current Income Tax Expense (Benefit)									17	9	10
Deferred Federal Income Tax Expense (Benefit)									423	454	270
Deferred Foreign Income Tax Expense (Benefit)									0	1	2
Deferred State and Local Income Tax Expense (Benefit)									30	32	39
Deferred Income Tax Expense (Benefit)									453	487	311
Income Tax Expense (Benefit)	$ 134	$ 130	$ 56	$ 150	$ 155	$ 144	$ 94	$ 103	$ 470	$ 496	$ 321