Income Tax Expense (Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax expense (benefit)	$ (17)	$ 34	$ (306)
Tax at statutory federal rate	62	19	7
Partnership earnings not subject to tax	(62)	(9)	(126)
Goodwill impairment	0	0	36
State and local tax, including federal expense (benefit)	(17)	24	(6)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	0	0	(225)
Other	0	0	8
Net income tax expense (benefit)	$ (30)	$ 4	$ 2