Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2012

Fair Value Measurements [Abstract]

Assets And Liabilities Measured At Fair Value On Recurring Basis

	Fair Value March  31, 2012		Quoted Prices in Active  Markets for Identical Assets (Level 1)		Significant  Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Recurring:
Investments in money market and short term treasury instruments	$	147,046	$	147,046	$	—	$	—
Retained interest in entities		10,817		—		—		10,817
Total, net	$	157,863	$	147,046	$	—	$	10,817

Fair value as of December 31, 2011:

	Fair Value December 31, 2011		Quoted Prices in Active  Markets for Identical Assets (Level 1)		Significant  Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Recurring:
Investments in money market and short term treasury instruments	$	148,985	$	148,985	$	—	$	—
Retained interest in entities		10,707		—		—		10,707
Total, net	$	159,692	$	148,985	$	—	$	10,707

Reconciliation Of Retained Interest

	2012
Balance, January 1	$	10,707
Additions		—
Accretion of interest income		110
Balance, March 31	$	10,817