Financial Information for the Company and Its Subsidiaries (Cash Flow Statements) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net cash flows provided by operating activities	$ 412,371	$ 332,824	$ 295,652
Cash flows from investing activities:
Acquisitions and related transactions	(2,184,058)	(73,594)	(277,388)
Acquisition of property and equipment	(40,217)	(28,856)	(28,864)
Proceeds from sale of interests in surgery centers	7,069	3,553	7,309
Purchases of marketable securities	(6,474)	0	0
Maturities of marketable securities	3,486	0	0
Other	(4,941)	159	0
Net cash flows used in investing activities	(2,225,135)	(98,738)	(298,943)
Cash flows from financing activities:
Proceeds from long-term borrowings	2,048,958	162,204	565,566
Repayment on long-term borrowings	(408,475)	(202,083)	(394,164)
Distributions to owners, including noncontrolling interests	(190,097)	(184,149)	(162,941)
Capital contributions	0		0
Proceeds from preferred stock offering	172,500	0	0
Cash dividends for preferred shares	(4,503)	0	0
Proceeds from common stock offering	439,875	0	0
Payments of equity issuance costs	(24,494)	0	0
Financing costs incurred	(65,811)	(1,322)	(7,982)
Changes in intercompany balances with affiliates, net	0	0	0
Other financing activities, net	2,050	(5,616)	510
Net cash flows provided by (used in) financing activities	1,970,003	(229,644)	8,971
Net increase in cash and cash equivalents	157,239	4,442	5,680
Cash and cash equivalents, beginning of year	50,840	46,398	40,718
Cash and cash equivalents, end of year	208,079	50,840	46,398
Consolidating Adjustments [Member]
Cash flows from operating activities:
Net cash flows provided by operating activities	(413,605)	(347,648)	(182,851)
Cash flows from investing activities:
Acquisitions and related transactions	2,126,737	694	92,830
Acquisition of property and equipment	0	0	0
Proceeds from sale of interests in surgery centers	0	0	0
Purchases of marketable securities	0
Maturities of marketable securities	0
Other	0	0
Net cash flows used in investing activities	2,126,737	694	92,830
Cash flows from financing activities:
Proceeds from long-term borrowings	0	0	0
Repayment on long-term borrowings	0	0	0
Distributions to owners, including noncontrolling interests	413,605	347,648	182,851
Capital contributions	(2,124,124)		(90,029)
Proceeds from preferred stock offering	0
Cash dividends for preferred shares	0
Proceeds from common stock offering	0
Payments of equity issuance costs	0
Financing costs incurred	0
Changes in intercompany balances with affiliates, net	0	0	0
Other financing activities, net	(2,613)	(694)	(2,801)
Net cash flows provided by (used in) financing activities	(1,713,132)	346,954	90,021
Net increase in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	0	0	0
Parent Company [Member]
Cash flows from operating activities:
Net cash flows provided by operating activities	96,681	45,127	(83,605)
Cash flows from investing activities:
Acquisitions and related transactions	(2,124,124)	0	(90,029)
Acquisition of property and equipment	(7,877)	(3,693)	(3,681)
Proceeds from sale of interests in surgery centers	0	0	0
Purchases of marketable securities	0
Maturities of marketable securities	0
Other	(3,068)	0
Net cash flows used in investing activities	(2,135,069)	(3,693)	(93,710)
Cash flows from financing activities:
Proceeds from long-term borrowings	2,040,000	152,700	560,000
Repayment on long-term borrowings	(396,493)	(188,081)	(381,220)
Distributions to owners, including noncontrolling interests	0	0	0
Capital contributions	0		0
Proceeds from preferred stock offering	172,500
Cash dividends for preferred shares	(4,503)
Proceeds from common stock offering	439,875
Payments of equity issuance costs	(24,494)
Financing costs incurred	(65,811)
Changes in intercompany balances with affiliates, net	2,965	88	(2,666)
Other financing activities, net	1,990	(6,690)	(70)
Net cash flows provided by (used in) financing activities	2,166,029	(41,983)	176,044
Net increase in cash and cash equivalents	127,641	(549)	(1,271)
Cash and cash equivalents, beginning of year	6,710	7,259	8,530
Cash and cash equivalents, end of year	134,351	6,710	7,259
Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash flows provided by operating activities	298,415	208,773	182,851
Cash flows from investing activities:
Acquisitions and related transactions	(2,188,191)	(74,288)	(280,189)
Acquisition of property and equipment	(9,933)	0	0
Proceeds from sale of interests in surgery centers	7,069	3,553	7,309
Purchases of marketable securities	0
Maturities of marketable securities	0
Other	(6,594)	159
Net cash flows used in investing activities	(2,197,649)	(70,576)	(272,880)
Cash flows from financing activities:
Proceeds from long-term borrowings	0	0	0
Repayment on long-term borrowings	0	0	0
Distributions to owners, including noncontrolling interests	(202,247)	(138,875)	0
Capital contributions	2,124,124		90,029
Proceeds from preferred stock offering	0
Cash dividends for preferred shares	0
Proceeds from common stock offering	0
Payments of equity issuance costs	0
Financing costs incurred	0
Changes in intercompany balances with affiliates, net	0	0	0
Other financing activities, net	828	678	0
Net cash flows provided by (used in) financing activities	1,922,705	(138,197)	90,029
Net increase in cash and cash equivalents	23,471	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	23,471	0	0
Non-Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash flows provided by operating activities	430,880	426,572	379,257
Cash flows from investing activities:
Acquisitions and related transactions	1,520	0	0
Acquisition of property and equipment	(22,407)	(25,163)	(25,183)
Proceeds from sale of interests in surgery centers	0	0	0
Purchases of marketable securities	(6,474)
Maturities of marketable securities	3,486
Other	4,721	0
Net cash flows used in investing activities	(19,154)	(25,163)	(25,183)
Cash flows from financing activities:
Proceeds from long-term borrowings	8,958	9,504	5,566
Repayment on long-term borrowings	(11,982)	(14,002)	(12,944)
Distributions to owners, including noncontrolling interests	(401,455)	(392,922)	(345,792)
Capital contributions	0		0
Proceeds from preferred stock offering	0
Cash dividends for preferred shares	0
Proceeds from common stock offering	0
Payments of equity issuance costs	0
Financing costs incurred	0
Changes in intercompany balances with affiliates, net	(2,965)	(88)	2,666
Other financing activities, net	1,845	1,090	3,381
Net cash flows provided by (used in) financing activities	(405,599)	(396,418)	(347,123)
Net increase in cash and cash equivalents	6,127	4,991	6,951
Cash and cash equivalents, beginning of year	44,130	39,139	32,188
Cash and cash equivalents, end of year	$ 50,257	$ 44,130	$ 39,139