Income Taxes Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income tax benefit (expense) at U.S. statutory rate	$ (58)	$ (640)	$ 831
Valuation allowance	(4)	529	(46)
Non-controlling interest	26	(6)	(6)
Goodwill impairment	(18)	0	(226)
Stock dispositions	69	0	0
Income not subject to taxation	14	220	(440)
Enactment of U.S. tax legislation, net of valuation allowance	0	392	0
Other	(25)	34	(25)
Income tax benefit	$ 4	$ 529	$ 88