Income Taxes - Schedule of Provision for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal - Current	$ 8,817	$ 3,351	$ 3,568
Federal - Deferred	(123)	(85)	(313)
Federal Income Tax Expense (Benefit), Continuing Operations	8,694	3,266	3,255
State - Current	97	131	158
State - Deferred	(20)	28	(21)
State and Local Income Tax Expense (Benefit), Continuing Operations	77	159	137
Foreign - Current	54	261	212
Foreign - Deferred	60	(77)	(51)
Foreign Income Tax Expense (Benefit), Continuing Operations	114	184	161
Provision for Income Taxes	$ 8,885	$ 3,609	$ 3,553