Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Current Federal Tax Expense (Benefit)	$ (743)	$ (929)	$ (1,872)
Current State and Local Tax Expense (Benefit)	1	29	(3)
Current foreign	55	84	129
Current Income Tax Expense (Benefit)	(687)	(816)	(1,746)
Deferred Federal Income Tax Expense (Benefit)	1,164	1,310	2,296
Deferred State and Local Income Tax Expense (Benefit)	(59)	(53)	37
Deferred foreign	(7)	17	11
Deferred Income Tax Expense (Benefit)	1,098	1,274	2,344
Other Tax Expense (Benefit)	(8)	(8)	(9)
Total income tax expense (benefit)	$ 403	$ 450	$ 589