Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Schedule of Marketable Securities

The following is a summary of available-for-sale marketable securities held as of December 31, 2018 and 2017 (in thousands):

			Gross Unrealized					Aggregate Fair Value		Classification on Balance Sheet
	Amortized Cost									Short-Term Marketable Securities		Long-Term Marketable Securities
As of December 31, 2018			Gains		Losses
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
As of December 31, 2017
Commercial paper	$	6,951	$	—	$	(9	)	$	6,942	$	6,942	$	—
Corporate bonds	736,902		2		(3,829		)	733,075		289,378		443,697
U.S. government agency obligations	220,014		—		(1,764		)	218,250		102,234		116,016
	$	963,867	$	2	$	(5,602	)	$	958,267	$	398,554	$	559,713

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 December 31, 2018 and 2017 (in thousands):

	Total Fair Value			Fair Value Measurements at Reporting Date Using
				Level 1		Level 2		Level 3
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 obligation related to completed acquisitions	$	(6,300	)	$	—	$	—	$	(6,300	)
As of December 31, 2017
Cash Equivalents and Marketable Securities:
Money market funds	$	22,649		$	22,649	$	—	$	—
Commercial paper	10,928			—		10,928		—
Corporate bonds	733,075			—		733,075		—
U.S. government agency obligations	218,248			—		218,248		—
Mutual funds	7,879			7,879		—		—
	$	992,779		$	30,528	$	962,251	$	—
Liabilities:
Contingent consideration obligation related to completed acquisitions	$	(8,631	)	$	—	$	—	$	(8,631	)

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 for the years ended December 31, 2018 and 2017 (in thousands):

	2018			2017
Beginning balance	$	(8,631	)	$	(7,100	)
Fair value adjustment to contingent consideration included in general and administrative expense	(1,835		)	(2,781		)
Cash paid upon achievement of milestone	4,166			1,250
Ending balance	$	(6,300	)	$	(8,631	)

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 December 31, 2018 and 2017 were as follows (in thousands):

	December 31, 2018		December 31, 2017
Due in 1 year or less	$	855,499	$	398,554
Due after 1 year through 5 years	199,257		559,713
	$	1,054,756	$	958,267