Cash and Cash Equivalents, Restricted Cash and Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2018

Cash and Cash Equivalents [Abstract]

Summary of Company's Cash and Cash Equivalents

The following table summarizes the Company’s cash and cash equivalents:

	June 30, 2018		December 31, 2017		Recurring Fair Value Measurement
	(in thousands)
Cash and cash equivalents:
Cash	$	20,112	$	24,092
Money market funds	142,684		251,950		Level 1
Commercial paper	13,309		9,831		Level 2
Total cash and cash equivalents	$	176,105	$	285,873

Summary of Company's Marketable Securities

The following tables summarize the Company’s marketable securities:

	June 30, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Recurring Fair Value Measurement
	(in thousands)
Fixed-income debt securities	$	15,679	$	19	$	(5	)	$	15,693	Level 2
Commercial paper	6,440		—		—			6,440		Level 2
U.S. treasuries	177,679		30		(3		)	177,706		Level 2
Total marketable securities	$	199,798	$	49	$	(8	)	$	199,839

	December 31, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Recurring Fair Value Measurement
	(in thousands)
Fixed-income debt securities	$	9,520	$	2	$	(15	)	$	9,507	Level 2
U.S. treasuries	2,249		—		(3		)	2,246		Level 2
Total marketable securities	$	11,769	$	2	$	(18	)	$	11,753

Summary of Contractual Maturities of Company's Marketable Securities

The following table presents the contractual maturities of the Company’s marketable securities:

	June 30, 2018				December 31, 2017
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(in thousands)
Mature within one year	$	199,798	$	199,839	$	11,519	$	11,504
Mature after one year and within three years	—		—		250		249
Total	$	199,798	$	199,839	$	11,769	$	11,753