Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Schedule of Marketable Securities

The following is a summary of available-for-sale marketable securities held as of June 30, 2019 and December 31, 2018 (in thousands):

			Gross Unrealized							Classification on Balance Sheet
	Amortized Cost		Gains		Losses			Aggregate Fair Value		Short-Term Marketable Securities		Long-Term Marketable Securities
As of June 30, 2019
Commercial paper	$	13,558	$	22	$	—		$	13,580	$	13,580	$	—
Corporate bonds	710,794		915		(691		)	711,018		442,522		268,496
U.S. government agency obligations	75,257		19		(57		)	75,219		70,215		5,004
	$	799,609	$	956	$	(748	)	$	799,817	$	526,317	$	273,500
As of December 31, 2018
Certificates of deposit	$	40,000	$	—	$	(7	)	$	39,993	$	39,993	$	—
Commercial paper	282,996		—		(50		)	282,946		282,946		—
Corporate bonds	685,653		1		(4,309		)	681,345		482,088		199,257
U.S. government agency obligations	50,876		—		(404		)	50,472		50,472		—
	$	1,059,525	$	1	$	(4,770	)	$	1,054,756	$	855,499	$	199,257

Schedule of Fair Value Measurement

The following table details the fair value measurements within the fair value hierarchy of the Company’s financial assets and liabilities as of June 30, 2019 and December 31, 2018 (in thousands):

	Total Fair Value			Fair Value Measurements at Reporting Date Using
				Level 1		Level 2		Level 3
As of June 30, 2019
Cash Equivalents and Marketable Securities:
Money market funds	$	2,550		$	2,550	$	—	$	—
Commercial paper	13,580			—		13,580		—
Corporate bonds	711,018			—		711,018		—
U.S. government agency obligations	75,219			—		75,219		—
Mutual funds	13,825			13,825		—		—
	$	816,192		$	16,375	$	799,817	$	—
As of December 31, 2018
Cash Equivalents and Marketable Securities:
Money market funds	$	380,260		$	380,260	$	—	$	—
Certificates of deposit	39,993			39,993		—		—
Commercial paper	282,946			—		282,946		—
Corporate bonds	681,345			—		681,345		—
U.S. government agency obligations	50,472			—		50,472		—
Mutual funds	10,016			10,016		—		—
	$	1,445,032		$	430,269	$	1,014,763	$	—
Liabilities:
Contingent consideration related to a completed acquisition	$	(6,300	)	$	—	$	—	$	(6,300	)

Schedule of Contractual Maturities of Marketable Securities and Other Investment Related Assets

Contractual maturities of the Company’s available-for-sale marketable securities held as of June 30, 2019 and December 31, 2018 were as follows (in thousands):

	June 30, 2019		December 31, 2018
Due in 1 year or less	$	526,317	$	855,499
Due after 1 year through 3 years	273,500		199,257
	$	799,817	$	1,054,756

Schedule of Activity of Major Classes of Assets Measured at Fair Value Using Level 3 Inputs

The following table reflects the activity for the Company’s major classes of liabilities measured at fair value using Level 3 inputs during the six months ended June 30, 2019 (in thousands):

	Other Liabilities: Contingent Consideration Obligation
Balance as of January 1, 2019	$	(6,300	)
Cash paid upon achievement of milestone	6,300
Balance as of June 30, 2019	$	—