Financial Instruments and Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2015

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, 2015 were as follows:

	Level 1		Level 2		Level 3		Total Fair Value
Cash equivalents:
Money market funds	$	23,406	$	—	$	—	$	23,406
Commercial paper	248,354		—		—		248,354
Debt securities:
U.S. Treasury securities	259,929		—		—		259,929
Corporate debt securities	—		101,193		—		101,193
Preferred stock	—		24,258		—		24,258
Restricted investments:
Guaranteed income fund	—		7,099		—		7,099
	$	531,689	$	132,550	$	—	$	664,239

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

	Level 1		Level 2		Level 3		Total Fair Value
Cash equivalents:
Money market funds	$	19,971	$	—	$	—	$	19,971
Debt securities:
U.S. Treasury securities	509,815		—		—		509,815
Corporate debt securities	—		100,105		—		100,105
Preferred stock	—		26,958		—		26,958
Restricted investments:
Guaranteed income fund	—		7,940		—		7,940
	$	529,786	$	135,003	$	—	$	664,789

Carrying Amount and Fair Value of Financial Instruments

The carrying amount and fair value of the Company’s financial instruments were as follows:

	March 31, 2015					December 31, 2014
	Carrying  value		Fair value		Level	Carrying  value		Fair value		Level
Assets
Pledged treasury securities	$	25,512	$	26,002	1	$	25,670	$	26,501	1
Retained interest investments	$	9,974	$	13,055	3	$	9,932	$	13,026	3
Investments held by special purpose entities (Note 5)	$	209,412	209,473		3	$	209,857	$	209,679	3
Liabilities
Senior Notes held by special purpose entity (Note 5)	$	177,366	177,966		3	$	177,341	$	177,940	3