Basis of Presentation (Details) (USD $)	Mar. 31, 2015 center	Dec. 31, 2014
Ownership Interests [Line Items]
Number of ownership interests of less than 51%	13
Restricted Cash and Marketable Securities
Restricted cash and marketable securities, total	$ 30,300,000
Restricted cash and marketable securities, current	10,957,000	10,219,000
Restricted cash and investments, noncurrent	19,300,000
Restricted marketable securities	$ 3,000,000
Consolidated [Member]
Ownership Interests [Line Items]
Number of ownership interests of less than 51%	2
Nonconsolidated [Member]
Ownership Interests [Line Items]
Number of ownership interests of less than 51%	11