Acquisitions (Narrative) (Details) (USD $)	3 Months Ended			3 Months Ended				0 Months Ended
	Mar. 31, 2014 Centers	Mar. 31, 2013 Centers	Dec. 31, 2013	Mar. 31, 2014 Noncontrolling Interest Number Of Centers [Member] Centers	Mar. 31, 2013 Noncontrolling Interest Number Of Centers [Member] Centers	Mar. 31, 2014 Controlling Interest [Member] Centers	Mar. 31, 2013 Controlling Interest [Member] Centers	Sep. 01, 2011 Acquired Nsc Centers [Member] Centers	Mar. 31, 2013 Acquired Nsc Centers [Member]	Mar. 31, 2014 Current Year Acquisitions [Member]	Mar. 31, 2013 Current Year Acquisitions [Member]
Business Acquisition [Line Items]
Equity Method Investments	$ 19,484,000		$ 16,392,000							$ 1,238,000	$ 5,200,000
Gain (loss) on deconsolidation	2,045,000	2,237,000
Number of business acquisitions				1	1	1	0	17
Payments to Acquire Businesses, Net of Cash Acquired	5,038,000	252,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High								7,500,000
Contingent Purchase Price Obligation, Settlement Amount									2,744,000
Goodwill deductible for tax purposes	4,670,000	0
Proceeds from Divestiture of Interest in Consolidated Subsidiaries	$ 600,000
Number Of Consolidated Centers Contributed To Joint Venture	1	1