Financial Information for the Company and Its Subsidiaries (Cash Flow Statements) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net cash flows provided by (used in) operating activities	$ 98,827	$ 69,819
Cash flows from investing activities:
Acquisitions and related expenses	(126,578)	(5,038)
Acquisition of property and equipment	(14,783)	(7,038)
Proceeds from sale of interests in surgery centers	0	1,111
Other	(220)	(418)
Net cash flows used in investing activities	(141,581)	(11,383)
Cash flows from financing activities:
Proceeds from long-term borrowings	2,227	31,945
Repayment on long-term borrowings	(5,213)us-gaap_RepaymentsOfLongTermDebt	(50,853)us-gaap_RepaymentsOfLongTermDebt
Distributions to owners, including noncontrolling interests	(47,202)us-gaap_PaymentsToMinorityShareholders	(43,194)us-gaap_PaymentsToMinorityShareholders
Capital contributions	0
Cash dividends for preferred shares	(2,264)	0
Changes in intercompany balances with affiliates, net	0amsg_ChangesInIntercompanyBalances	0amsg_ChangesInIntercompanyBalances
Other financing activities, net	3,283	(58)
Net cash flows used in financing activities	(49,169)	(62,160)
Net decrease in cash and cash equivalents	(91,923)	(3,724)
Cash and cash equivalents, beginning of period	208,079	50,840
Cash and cash equivalents, end of period	116,156	47,116
Consolidation, Eliminations [Member]
Cash flows from operating activities:
Net cash flows provided by (used in) operating activities	(62,196)	(93,016)
Cash flows from investing activities:
Acquisitions and related expenses	62,525	44
Acquisition of property and equipment	0	0
Proceeds from sale of interests in surgery centers		0
Other	0	0
Net cash flows used in investing activities	62,525	44
Cash flows from financing activities:
Proceeds from long-term borrowings	0	0
Repayment on long-term borrowings	0	0
Distributions to owners, including noncontrolling interests	62,196	93,016
Capital contributions	(62,056)
Cash dividends for preferred shares	0
Changes in intercompany balances with affiliates, net	0	0
Other financing activities, net	(469)	(44)
Net cash flows used in financing activities	(329)	92,972
Net decrease in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Parent Company [Member]
Cash flows from operating activities:
Net cash flows provided by (used in) operating activities	(33,779)	18,482
Cash flows from investing activities:
Acquisitions and related expenses	(62,056)	0
Acquisition of property and equipment	(2,678)	(1,237)
Proceeds from sale of interests in surgery centers		0
Other	0	(629)
Net cash flows used in investing activities	(64,734)	(1,866)
Cash flows from financing activities:
Proceeds from long-term borrowings	0	30,000
Repayment on long-term borrowings	(2,175)	(47,679)
Distributions to owners, including noncontrolling interests	0	0
Capital contributions	0
Cash dividends for preferred shares	(2,264)
Changes in intercompany balances with affiliates, net	(2,573)	556
Other financing activities, net	1,292	(641)
Net cash flows used in financing activities	(5,720)	(17,764)
Net decrease in cash and cash equivalents	(104,233)	(1,148)
Cash and cash equivalents, beginning of period	134,351	6,710
Cash and cash equivalents, end of period	30,118	5,562
Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash flows provided by (used in) operating activities	91,981	48,096
Cash flows from investing activities:
Acquisitions and related expenses	(127,047)	(5,082)
Acquisition of property and equipment	(2,538)	0
Proceeds from sale of interests in surgery centers		1,111
Other	(1,322)	211
Net cash flows used in investing activities	(130,907)	(3,760)
Cash flows from financing activities:
Proceeds from long-term borrowings	0	0
Repayment on long-term borrowings	0	0
Distributions to owners, including noncontrolling interests	(10,241)	(44,920)
Capital contributions	62,056
Cash dividends for preferred shares	0
Changes in intercompany balances with affiliates, net	0	0
Other financing activities, net	2,321	584
Net cash flows used in financing activities	54,136	(44,336)
Net decrease in cash and cash equivalents	15,210	0
Cash and cash equivalents, beginning of period	23,471	0
Cash and cash equivalents, end of period	38,681	0
Non-Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash flows provided by (used in) operating activities	102,821	96,257
Cash flows from investing activities:
Acquisitions and related expenses	0	0
Acquisition of property and equipment	(9,567)	(5,801)
Proceeds from sale of interests in surgery centers		0
Other	1,102	0
Net cash flows used in investing activities	(8,465)	(5,801)
Cash flows from financing activities:
Proceeds from long-term borrowings	2,227	1,945
Repayment on long-term borrowings	(3,038)	(3,174)
Distributions to owners, including noncontrolling interests	(99,157)	(91,290)
Capital contributions	0
Cash dividends for preferred shares	0
Changes in intercompany balances with affiliates, net	2,573	(556)
Other financing activities, net	139	43
Net cash flows used in financing activities	(97,256)	(93,032)
Net decrease in cash and cash equivalents	(2,900)	(2,576)
Cash and cash equivalents, beginning of period	50,257	44,130
Cash and cash equivalents, end of period	$ 47,357	$ 41,554

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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The net cash outflow or inflow from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.

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Amount of cash outflow in the form of ordinary dividends to preferred shareholders of the parent entity.

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The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

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