Income Taxes (Schedule of Reconciliation between the Statutory Federal Income Tax Rate and the Effective Tax Rate) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Differences between the statutory federal income tax rate and the effective tax rate
Benefit for income taxes at statutory federal rate, Amount	$ (150)	$ (991)	$ (600)
State income taxes, net of federal income tax benefit, Amount	(114)	(10)	(1)
Net income attributable to noncontrolling interests, Amount	(18)	(22)	(33)
Change in valuation allowance, Amount	212	26	(1)
Change in uncertain tax position, Amount	9
Federal rate change, Amount		32
Federal and state tax credits, Amount	(17)	(5)	(6)
Nondeductible transaction costs, Amount			3
Nondeductible goodwill, Amount	30	504	536
Nondeductible settlments, Amount	22
Other, Amount	15	17	(2)
Total benefit from income taxes for loss from continuing operations	$ (11)	$ (449)	$ (104)
Provision for income taxes at statutory federal rate, Percentage	21.00%	35.00%	35.00%
State income taxes, net of federal income tax benefit, Percentage	16.00%	0.30%	0.10%
Net income attributable to noncontrolling interests, Percentage	2.50%	0.80%	1.90%
Change in valuation allowance, Percentage	(29.70%)	(0.90%)	0.10%
Change in uncertain tax position, Percentage	(1.30%)
Federal rate change, Percentage		(1.10%)
Federal and state tax credits, Percentage	2.40%	0.10%	0.30%
Nondeductible transaction costs, Percentage			(0.20%)
Nondeductible goodwill, Percentage	(4.20%)	(17.80%)	(31.20%)
Nondeductible settlements, Percentage	(3.10%)
Other, Percentage	(2.10%)	(0.60%)	0.10%
Benefit from income taxes from continuing operations, Percentage	1.50%	15.80%	6.10%