Fair Value Measurements (Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Investments in money market and short term treasury instruments	$ 186,873	$ 177,816
Retained interest in entities	10,490	10,283
Total, net	197,363	188,099
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Investments in money market and short term treasury instruments	186,873	177,816
Retained interest in entities
Total, net	186,873	177,816
Significant Other Observable Inputs (Level 2) [Member]
Investments in money market and short term treasury instruments
Retained interest in entities
Total, net
Significant Unobservable Inputs (Level 3) [Member]
Investments in money market and short term treasury instruments
Retained interest in entities	10,490	10,283
Total, net	$ 10,490	$ 10,283