Stockholders' Equity (Schedule of Stockholders' Equity) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2015 USD ($)
Equity, beginning balance	$ 4,083
Redeemable Noncontrolling Interests, beginning balance	531
Comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interests	198
Distributions to noncontrolling interests, net of contributions	(14)
Purchase of subsidiary shares from noncontrolling interests	(8)
Other reclassifications of noncontrolling interests	1
Adjustment to redemption value of redeemable noncontrolling interests	(8)
Issuance of common stock in connection with the exercise of stock options	22
Cancellation of restricted stock for tax withholdings on vested shares	(20)
Share-based compensation	30
Equity, ending balance	4,284
Redeemable Noncontrolling Interests, ending balance	524
Redeemable Noncontrolling Interests (Non- Equity) [Member]
Redeemable Noncontrolling Interests, beginning balance	531
Comprehensive income (loss) attributable to redeemable noncontrolling interest	33
Distributions to redeemable noncontrolling interests, net of contributions	(34)
Purchase of subsidiary shares from noncontrolling interests	(5)
Disposition of less-than-wholly owned hospital owned hospital	(8)
Other reclassifications of redeemable noncontrolling interests	(1)
Adjustment to redemption value of redeemable noncontrolling interests	8
Redeemable Noncontrolling Interests, ending balance	524
Common Stock [Member]
Equity, beginning balance	1
Equity, ending balance	1
Additional Paid-in Capital [Member]
Equity, beginning balance	2,095
Purchase of subsidiary shares from noncontrolling interests	(14)
Adjustment to redemption value of redeemable noncontrolling interests	(8)
Issuance of common stock in connection with the exercise of stock options	22
Cancellation of restricted stock for tax withholdings on vested shares	(20)
Share-based compensation	30
Equity, ending balance	2,105
Treasury Stock [Member]
Equity, beginning balance	(7)
Equity, ending balance	(7)
Accumulated Other Comprehensive (Loss) Income [Member]
Equity, beginning balance	(63)
Comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interests	(1)
Equity, ending balance	(64)
Retained Earnings [Member]
Equity, beginning balance	1,977
Comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interests	189
Equity, ending balance	2,166
Noncontrolling Interests [Member]
Equity, beginning balance	80
Comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interests	10
Distributions to noncontrolling interests, net of contributions	(14)
Purchase of subsidiary shares from noncontrolling interests	6
Other reclassifications of noncontrolling interests	1
Equity, ending balance	$ 83