Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2018

Investments Debt And Equity Securities [Abstract]

Schedule of Investments

The table below summarizes the Company’s investments (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized			Estimated
	Cost		Gains		(Losses)			Fair Value
September 30, 2018
Cash equivalents:
Money market funds	$	18	$	—	$	—		$	18
Total		18		—		—			18
Available-for-sale securities:
Commercial paper securities		317,203		11		(95	)		317,119
Corporate debt securities		83,684		—		(105	)		83,579
U.S. government-sponsored entity debt securities		18,598		—		(24	)		18,574
Total		419,485		11		(224	)		419,272
Total cash equivalents and available-for-sale securities	$	419,503	$	11	$	(224	)	$	419,290
December 31, 2017
Cash equivalents:
Money market funds	$	24,290	$	—	$	—		$	24,290
Commercial paper securities		4,595		—		—			4,595
Total		28,885		—		—			28,885
Available-for-sale securities:
Commercial paper securities		110,365		—		(118	)		110,247
Corporate debt securities		75,886		—		(131	)		75,755
U.S. government-sponsored entity debt securities		8,498		—		(6	)		8,492
Total		194,749		—		(255	)		194,494
Total cash equivalents and available-for-sale securities	$	223,634		—	$	(255	)	$	223,379