Stockholders' Deficit (Schedule of Stockholders' Deficit) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Equity, beginning balance	$ (2,141)	$ (1,463)
Redeemable Noncontrolling Interests, beginning balance	502
Comprehensive income (loss)	28	(110)
Distributions to noncontrolling interests	(8)	(8)
Purchase of subsidiary shares from noncontrolling interests	(1)
Other reclassifications of noncontrolling interests	(8)	1
Adjustment to redemption value of redeemable noncontrolling interests	(7)	(12)
Cancellation of restricted stock for tax withholdings on vested shares	(1)	(1)
Share-based compensation	2	3
Equity, ending balance	(2,136)	(1,590)
Redeemable Noncontrolling Interests, ending balance	502
Redeemable Noncontrolling Interests (Non- Equity) [Member]
Redeemable Noncontrolling Interests, beginning balance	502	504
Comprehensive income (loss) attributable to redeemable noncontrolling interest	8	9
Contributions from redeemable noncontrolling interests		1
Distributions to redeemable noncontrolling interests	(22)	(19)
Purchase of subsidiary shares from noncontrolling interests	(1)	(1)
Other reclassifications of redeemable noncontrolling interests	8	(1)
Adjustment to redemption value of redeemable noncontrolling interests	7	12
Redeemable Noncontrolling Interests, ending balance	502	505
Common Stock [Member]
Equity, beginning balance	1	1
Equity, ending balance	1	1
Additional Paid-in Capital [Member]
Equity, beginning balance	2,008	2,017
Purchase of subsidiary shares from noncontrolling interests	(1)
Adjustment to redemption value of redeemable noncontrolling interests	(7)	(12)
Cancellation of restricted stock for tax withholdings on vested shares	(1)	(1)
Share-based compensation	2	3
Equity, ending balance	2,001	2,007
Accumulated Other Comprehensive Income (Loss) [Member]
Equity, beginning balance	(9)	(10)
Comprehensive income (loss)	2
Equity, ending balance	(7)	(10)
Accumulated Deficit [Member]
Equity, beginning balance	(4,218)	(3,543)
Comprehensive income (loss)	18	(118)
Equity, ending balance	(4,200)	(3,661)
Noncontrolling Interest [Member]
Equity, beginning balance	77	72
Comprehensive income (loss)	8	8
Distributions to noncontrolling interests	(8)	(8)
Other reclassifications of noncontrolling interests	(8)	1
Equity, ending balance	$ 69	$ 73