Income Taxes (Schedule of Earnings Before Income Taxes and Provision for Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
United States	$ 9,809	$ 21,867	$ 8,078
Outside United States	19	(15)	0
Earnings before income taxes	9,828	21,852	8,078
Current:
Federal	2,346	4,093	2,516
State and local	366	390	451
Outside United States	15	6	0
Total current provision for income taxes	2,727	4,489	2,967
Deferred:
Federal	(3,213)	3,102	(140)
State and local	86	20	8
Outside United States	1	(3)	0
Total deferred provision for income taxes	(3,126)	3,119	(132)
Total (benefit) provision for income taxes	$ (399)	$ 7,608	$ 2,835