Financial Instruments and Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2014

Fair Value Disclosures [Abstract]

Schedule of Financial Instruments Measured at Fair Value on a Recurring Basis

The financial instruments measured at fair value on a recurring basis at March 31, 2014 were as follows:

	Level 1		Level 2		Level 3		Total Fair Value
Money market funds	$	7,073	$	—	$	—	$	7,073
U.S. Treasury securities	209,997		—		—		209,997
Debt securities:
U.S. Treasury securities	224,842		—		—		224,842
Corporate debt securities	—		53,575		—		53,575
Preferred stock	—		3,373		—		3,373
	$	441,912	$	56,948	$	—	$	498,860

The financial instruments measured at fair value on a recurring basis at December 31, 2013 were as follows:

	Level 1		Level 2		Level 3		Total Fair Value
Money market funds	$	1,761	$	—	$	—	$	1,761
Debt securities:
U.S. Treasury securities	124,949		—		—		124,949
Corporate debt securities	—		22,023		—		22,023
	$	126,710	$	22,023	$	—	$	148,733

Carrying Amount and Fair Value of Financial Instruments

The carrying amount and fair value of the Company’s financial instruments were as follows (the table below excludes financial instruments with carrying values that approximate their fair values):

	March 31, 2014					December 31, 2013
	Carrying  value		Fair value		Level	Carrying  value		Fair value		Level
Assets
Pledged treasury securities	$	26,111	$	28,008	1	$	26,260	$	28,465	1
Retained interest investments	$	9,684	$	12,875	3	$	9,639	$	12,827	3