Fair Value Measurements (Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments in money market and short term treasury instruments	$ 147,046	$ 148,985
Retained interest in entities	10,817	10,707
Total, net	157,863	159,692
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments in money market and short term treasury instruments	147,046	148,985
Total, net	147,046	148,985
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments in money market and short term treasury instruments
Retained interest in entities
Total, net
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Retained interest in entities	10,817	10,707
Total, net	$ 10,817	$ 10,707