Fair value measurements (Tables)

6 Months Ended

Jun. 30, 2012

Assets and Liabilities Measured at Fair Value on Recurring Basis

Assets and liabilities measured at fair value on a recurring basis are as follows:

Fair value as of June 30, 2012:

	Fair Value June 30, 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	$	152,109	$	152,109	$	—	$	—
Retained interest in entities		10,928		—		—		10,928
Total, net	$	163,037	$	152,109	$	—	$	10,928

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

The following is a reconciliation of the Company’s retained interest:

	2012
Balance, January1	$	10,707
Additions		—
Accretion of interest income		221
Balance, June 30	$	10,928