Stockholders' Equity (Schedule of Stockholders' Equity) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Equity, beginning balance	$ 4,083
Redeemable Noncontrolling Interests, beginning balance	531
Comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interests	76
Distributions to noncontrolling interests, net of contributions	(6)
Other reclassifications of noncontrolling interests	1
Adjustment to redemption value of redeemable noncontrolling interests	(6)
Issuance of common stock in connection with the exercise of stock options	18
Cancellation of restricted stock for tax withholdings on vested shares	(20)
Share-based compensation	14
Equity, ending balance	4,160
Redeemable Noncontrolling Interests, ending balance	520
Redeemable Noncontrolling Interests (Non- Equity) [Member]
Redeemable Noncontrolling Interests, beginning balance	531
Comprehensive income (loss) attributable to redeemable noncontrolling interest	16
Distributions to redeemable noncontrolling interests, net of contributions	(17)
Purchase of subsidiary shares from noncontrolling interests	(7)
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	6
Redeemable Noncontrolling Interests, ending balance	520
Common Stock [Member]
Equity, beginning balance		1
Equity, ending balance	1	1
Additional Paid-in Capital [Member]
Equity, beginning balance	2,095
Adjustment to redemption value of redeemable noncontrolling interests	(6)
Issuance of common stock in connection with the exercise of stock options	18
Cancellation of restricted stock for tax withholdings on vested shares	(20)
Share-based compensation	14
Equity, ending balance	2,101
Treasury Stock [Member]
Equity, beginning balance		(7)
Equity, ending balance	(7)	(7)
Accumulated Other Comprehensive (Loss) Income [Member]
Equity, beginning balance	(63)
Comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interests	(7)
Equity, ending balance	(70)
Retained Earnings [Member]
Equity, beginning balance	1,977
Comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interests	79
Equity, ending balance	2,056
Noncontrolling Interests [Member]
Equity, beginning balance	80
Comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interests	4
Distributions to noncontrolling interests, net of contributions	(6)
Other reclassifications of noncontrolling interests	1
Equity, ending balance	$ 79