Income Taxes - Income Tax Provision (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current tax (provision) benefit:
Federal	$ (4)	$ 0	$ (23)
State and local	5	(28)	(25)
International	(54)	(12)	(2)
Deferred tax provision:
Federal	(1,911)	(2,080)	(2,409)
State and local	(160)	(143)	(172)
Income Tax (Provision) Benefit	$ (2,124)	$ (2,263)	$ (2,631)