Stockholders' Deficit (Schedule of Stockholders' Deficit) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Deficit, beginning balance	$ (692)
Redeemable Noncontrolling Interests, beginning balance	527
Comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interests	(2)
Distributions to noncontrolling interests, net of contributions	(6)
Purchase of subsidiary shares from noncontrolling interests	(2)
Other reclassifications of noncontrolling interests	(1)
Cancellation of restricted stock for tax withholdings on vested shares	(2)
Stock-based compensation	4
Deficit, ending balance	(701)
Redeemable Noncontrolling Interests, ending balance	523
Redeemable Noncontrolling Interests [Member]
Redeemable Noncontrolling Interests, beginning balance	527
Comprehensive income (loss) attributable to redeemable noncontrolling interest	13
Distributions to redeemable noncontrolling interests, net of contributions	(17)
Purchase of subsidiary shares from noncontrolling interests	(1)
Other reclassifications of redeemable noncontrolling interests	1
Redeemable Noncontrolling Interests, ending balance	523
Common Stock [Member]
Deficit, beginning balance	1
Deficit, ending balance	1
Additional Paid-in Capital [Member]
Deficit, beginning balance	2,014
Purchase of subsidiary shares from noncontrolling interests	(2)
Cancellation of restricted stock for tax withholdings on vested shares	(2)
Stock-based compensation	4
Deficit, ending balance	2,014
Accumulated Other Comprehensive Income (Loss) [Member]
Deficit, beginning balance	(21)
Comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interests	17
Adoption of new accounting standards	(12)
Deficit, ending balance	(16)
Retained Earnings (Accumulated Deficit) [Member]
Deficit, beginning balance	(2,761)
Comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interests	(25)
Adoption of new accounting standards	12
Deficit, ending balance	(2,774)
Noncontrolling Interests [Member]
Deficit, beginning balance	75
Comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interests	6
Distributions to noncontrolling interests, net of contributions	(6)
Other reclassifications of noncontrolling interests	(1)
Deficit, ending balance	$ 74