Stockholders' Equity (Schedule of Stockholders' Equity) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Equity, beginning balance	$ 4,105
Redeemable Noncontrolling Interests, beginning balance	571
Comprehensive income including portion attributable to nonredeemable noncontrolling interests	1
Distributions to noncontrolling interests, net of contributions	(4)
Purchase of subsidiary shares from noncontrolling interests	(6)
Other reclassifications of noncontrolling interests	1
Noncontrolling interests in acquired entity	29
Income tax payable increase from vesting of restricted shares	(15)
Cancellation of restricted stock for tax withholdings on vested shares	(7)
Share-based compensation	14
Equity, ending balance	4,118
Redeemable Noncontrolling Interests, ending balance	565
Redeemable Noncontrolling Interests (Non- Equity) [Member]
Redeemable Noncontrolling Interests, beginning balance	571
Comprehensive income attributable to redeemable noncontrolling interest	19
Distributions to redeemable noncontrolling interests, net of contributions	(14)
Purchase of subsidiary shares from noncontrolling interests	(10)
Other reclassifications of redeemable noncontrolling interests	(1)
Redeemable Noncontrolling Interests, ending balance	565
Common Stock [Member]
Equity, beginning balance	1
Equity, ending balance	1
Additional Paid-in Capital [Member]
Equity, beginning balance	1,963
Purchase of subsidiary shares from noncontrolling interests	(3)
Income tax payable increase from vesting of restricted shares	(15)
Cancellation of restricted stock for tax withholdings on vested shares	(7)
Share-based compensation	14
Equity, ending balance	1,952
Treasury Stock [Member]
Equity, beginning balance	(7)
Equity, ending balance	(7)
Accumulated Other Comprehensive (Loss) Income [Member]
Equity, beginning balance	(73)
Comprehensive income including portion attributable to nonredeemable noncontrolling interests	(16)
Equity, ending balance	(89)
Retained Earnings [Member]
Equity, beginning balance	2,135
Comprehensive income including portion attributable to nonredeemable noncontrolling interests	11
Equity, ending balance	2,146
Noncontrolling Interests [Member]
Equity, beginning balance	86
Comprehensive income including portion attributable to nonredeemable noncontrolling interests	6
Distributions to noncontrolling interests, net of contributions	(4)
Purchase of subsidiary shares from noncontrolling interests	(3)
Other reclassifications of noncontrolling interests	1
Noncontrolling interests in acquired entity	29
Equity, ending balance	$ 115