Financial Instruments and Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

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 December 31, 2017 were as follows:

	Level 1		Level 2		Level 3		Total Fair Value
Cash equivalents:
Money market funds	$	10,505	$	—	$	—	$	10,505
Commercial paper	159,970		—		—		159,970
	170,475		—		—		170,475
Investments:
U.S. Treasury securities	9,870		—		—		9,870
Corporate debt securities	—		66,375		—		66,375
Preferred stock	10,717		24,306		—		35,023
	20,587		90,681		—		111,268
Restricted investments:
Short-term bond	4,251		—		—		4,251
Money market fund	218		—		—		218
	4,469		—		—		4,469
	$	195,531	$	90,681	$	—	$	286,212

The financial instruments measured at fair value on a recurring basis at December 31, 2016 were as follows:

	Level 1		Level 2		Level 3		Total Fair Value
Cash equivalents:
Money market funds	$	86,236	$	—	$	—	$	86,236
Commercial paper	129,671		—		—		129,671
	215,907		—		—		215,907
Investments:
Corporate debt securities	57,788		81,344		—		139,132
Preferred stock	19,177		17,416		—		36,593
	76,965		98,760		—		175,725
Restricted investments:
Short-term bond	4,226		—		—		4,226
Money market fund	1,410		—		—		1,410
	5,636		—		—		5,636
	$	298,508	$	98,760	$	—	$	397,268

Carrying Amount and Fair Value of Financial Instruments

The carrying amount and fair value, measured on a nonrecurring basis, of the Company’s financial instruments were as follows:

	December 31, 2017					December 31, 2016
	Carrying  value		Fair value		Level	Carrying  value		Fair value		Level
Assets
Retained interest investments	$	11,147	$	14,106	3	$	10,635	$	13,669	3
Investments held by SPEs:
Time deposit	$	200,000	$	200,000	3	$	200,000	$	200,000	3
U.S. Treasury securities and cash equivalents	$	7,989	$	7,797	1	$	8,590	$	8,398	1
Liabilities
Senior Notes held by SPE	$	176,537	$	198,530	3	$	176,310	$	199,691	3