Acquisitions (Fair Value Of Total Consideration Transferred And Major Class Of Consideration) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Acquired Nsc Centers [Member]
Business Acquisition [Line Items]
Accounts receivable	$ 16,032
Supplies, inventory, prepaid and other current assets	5,744
Investment in unconsolidated affiliates	10,710
Property and equipment	18,208
Goodwill	167,865
Other intangible assets	268
Accounts payable	(2,612)
Other accrued liabilities	(5,233)
Long-term debt	(2,900)
Other long-term liabililties	(1,895)
Total fair value	206,187
Less: Fair value attributable to noncontrolling interests	70,502
Acquisition date fair value of total consideration transferred	135,685
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Accounts receivable	7,837	2,471
Supplies, inventory, prepaid and other current assets	1,888	1,072
Investment in unconsolidated affiliates	0	0
Property and equipment	8,350	4,291
Goodwill	169,777	86,852
Other intangible assets	1,750	0
Accounts payable	(2,665)	(946)
Other accrued liabilities	(415)	(198)
Long-term debt	(5,698)	(2,410)
Other long-term liabililties	0	0
Total fair value	180,824	91,132
Less: Fair value attributable to noncontrolling interests	72,050	33,547
Acquisition date fair value of total consideration transferred	$ 108,774	$ 57,585