Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Current Federal Tax Expense (Benefit)	$ (929)	$ (1,872)	$ (985)
Current State and Local Tax Expense (Benefit)	29	(3)	(2)
Current foreign	84	129	121
Current Income Tax Expense (Benefit)	(816)	(1,746)	(866)
Deferred Federal Income Tax Expense (Benefit)	1,310	2,296	1,306
Deferred State and Local Income Tax Expense (Benefit)	(53)	37	(247)
Deferred foreign	17	11	(59)
Deferred Income Tax Expense (Benefit)	1,274	2,344	1,000
Other Tax Expense (Benefit)	(8)	(9)	(4)
Total income tax expense (benefit)	$ 450	$ 589	$ 130