Stockholders' Equity (Schedule of Stockholders' Equity) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)
Equity, beginning balance	$ 1,728
Redeemable Noncontrolling Interests, beginning balance	554
Comprehensive income including portion attributable to nonredeemable noncontrolling interests	(417)
Contributions from noncontrolling interests	5
Distributions to noncontrolling interests, net of contributions	(22)
Disposition of less-than-wholly owned entity	(10)
Other reclassifications of noncontrolling interests	(2)
Adjustment to redemption value of redeemable noncontrolling interests	12
Cancellation of restricted stock for tax withholdings on vested shares	(5)
Stock-based compensation	20
Equity, ending balance	1,309
Redeemable Noncontrolling Interests, ending balance	530
Redeemable Noncontrolling Interests [Member]
Redeemable Noncontrolling Interests, beginning balance	554
Comprehensive income attributable to redeemable noncontrolling interest	44
Distributions to redeemable noncontrolling interests, net of contributions	(57)
Purchase of subsidiary shares from noncontrolling interests	(4)
Disposition of less-than-wholly owned entity	2
Other reclassifications of redeemable noncontrolling interests	2
Noncontrolling interests in acquired entity	1
Adjustment to redemption value of redeemable noncontrolling interests	(12)
Equity, ending balance	530
Redeemable Noncontrolling Interests, ending balance
Common Stock [Member]
Equity, beginning balance	1
Equity, ending balance	1
Additional Paid-in Capital [Member]
Equity, beginning balance	1,975
Adjustment to redemption value of redeemable noncontrolling interests	12
Cancellation of restricted stock for tax withholdings on vested shares	(5)
Stock-based compensation	20
Equity, ending balance	2,002
Accumulated Other Comprehensive Income (Loss) [Member]
Equity, beginning balance	(62)
Comprehensive income including portion attributable to nonredeemable noncontrolling interests	17
Equity, ending balance	(45)
Retained Earnings (Accumulated Deficit) [Member]
Equity, beginning balance	(299)
Comprehensive income including portion attributable to nonredeemable noncontrolling interests	(446)
Equity, ending balance	(745)
Noncontrolling Interests [Member]
Equity, beginning balance	113
Comprehensive income including portion attributable to nonredeemable noncontrolling interests	12
Contributions from noncontrolling interests	5
Distributions to noncontrolling interests, net of contributions	(22)
Disposition of less-than-wholly owned entity	(10)
Other reclassifications of noncontrolling interests	(2)
Equity, ending balance	$ 96