Financial Instruments and Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Financial Instruments and Fair Value Measurements

Schedule of Financial Instruments Measured at Fair Value on Recurring Basis

The financial instruments measured at fair value on a recurring basis are as follows:

	December 31, 2018
							Total Fair
	Level 1		Level 2		Level 3		Value
Cash equivalents:
Money market funds	$	43,346	$	—	$	—	$	43,346
Commercial paper		107,586		—		—		107,586
U.S. Treasury securities		29,998		—		—		29,998
		180,930		—		—		180,930
Investments - debt securities:
U.S. Treasury securities		6,937		—		—		6,937
Corporate debt securities		—		2,021		—		2,021
		6,937		2,021		—		8,958
Investments - equity securities:
Preferred stock		10,470		25,662		—		36,132
Restricted investments:
Short-term bond		3,265		—		—		3,265
Money market fund		167		—		—		167
		3,432		—		—		3,432
	$	201,769	$	27,683	$	—	$	229,452

	December 31, 2017
							Total Fair
	Level 1		Level 2		Level 3		Value
Cash equivalents:
Money market funds	$	10,505	$	—	$	—	$	10,505
Commercial paper		159,970		—		—		159,970
		170,475		—		—		170,475
Investments - debt securities:
U.S. Treasury securities		9,870		—		—		9,870
Corporate debt securities		—		66,375		—		66,375
		9,870		66,375		—		76,245
Investments - equity securities:
Preferred stock		10,717		24,306		—		35,023
Restricted investments:
Short-term bond		4,251		—		—		4,251
Money market fund		218		—		—		218
		4,469		—		—		4,469
	$	195,531	$	90,681	$	—	$	286,212

Schedule of Carrying Amount and Fair Value Measured on Nonrecurring Basis of Financial Instruments

	December 31, 2018					December 31, 2017
	Carrying					Carrying
	value		Fair value		Level	value		Fair value		Level
Assets
Investments held by SPEs:
Time deposit	$	200,000	$	200,000	3	$	200,000	$	200,000	3
U.S. Treasury securities and cash	$	7,384	$	7,092	1	$	7,989	$	7,797	1
Liabilities
Senior Notes held by SPE	$	176,775	$	193,293	3	$	176,537	$	198,530	3