Financial Instruments and Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 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 June 30, 2014 were as follows:

	Level 1		Level 2		Level 3		Total Fair Value
Money market funds	$	34,151	$	—	$	—	$	34,151
Debt securities:
U.S. Treasury securities	524,814		—		—		524,814
Corporate debt securities	—		100,241		—		100,241
Preferred stock	—		3,487		—		3,487
	$	558,965	$	103,728	$	—	$	662,693

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):

	June 30, 2014					December 31, 2013
	Carrying  value		Fair value		Level	Carrying  value		Fair value		Level
Assets
Pledged treasury securities	$	25,967	$	27,520	1	$	26,260	$	28,465	1
Retained interest investments	$	9,782	$	13,049	3	$	9,639	$	12,827	3