Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2017

Marketable Securities

Summary of marketable securities portfolio

The following is a summary of our marketable security portfolio as of December 31, 2017 and 2016, respectively.

			Net		Net
	Amortized		Unrealized		Unrealized		Estimated
	Cost		Gains		Losses		Fair Value
	(in thousands)
December 31, 2017
Debt securities (corporate and government)	$	271,401	$	—	$	(1,265)	$	270,136
December 31, 2016
Debt securities (corporate and government)	$	156,330	$	—	$	(127)	$	156,203

Schedule of fair value of assets and liabilities measured on recurring basis

The following fair value hierarchy table presents information about each major category of our financial assets measured at fair value on a recurring basis as of December 31, 2017 (in thousands):

	Fair Value Measurement at Reporting Date Using:
	Quoted Prices in		Significant Other		Significant
	Active Markets for		Observable		Unobservable
	Identical Assets		Inputs		Inputs		Balance as of
	(Level 1)		(Level 2)		(Level 3)		December 31, 2017
Cash and cash equivalents	$	899,509	$	—	$	—	$	899,509
Debt securities (corporate and government)		—		270,136		—		270,136
Long term investments (Note 6)		134,356		—		—		134,356
Total assets	$	1,033,865	$	270,136	$	—	$	1,304,001

The following fair value hierarchy table presents information about each major category of our financial liabilities measured at fair value on a recurring basis as of December 31, 2017 (in thousands):

	Fair Value Measurement at Reporting Date Using:
	Quoted Prices in		Significant Other		Significant
	Active Markets for		Observable		Unobservable
	Identical Assets		Inputs		Inputs		Balance as of
	(Level 1)		(Level 2)		(Level 3)		December 31, 2017
Contingent consideration (Note 2)	$	—	$	—	$	287,000	$	287,000
Total liabilities	$	—	$	—	$	287,000	$	287,000

Schedule of rollforward of Level 3 liabilities

The following is a roll forward of our Level 3 liabilities (in thousands):

	Level 3
Balance at January 1, 2017	$	301,000
Contingent consideration earned during the period but not yet paid		(6,618)
Payments made during the period		(15,086)
Change in fair value of contingent consideration		7,704
Balance at December 31, 2017	$	287,000

Schedule of fair value of assets measured on recurring basis

The following fair value hierarchy table presents information about each major category of our financial assets measured at fair value on a recurring basis as of December 31, 2016 (in thousands):

	Fair Value Measurement at Reporting Date Using:
	Quoted Prices in		Significant Other		Significant
	Active Markets for		Observable		Unobservable
	Identical Assets		Inputs		Inputs		Balance as of
	(Level 1)		(Level 2)		(Level 3)		December 31, 2016
Cash and cash equivalents	$	652,343	$	—	$	—	$	652,343
Debt securities (corporate and government)		—		156,203		—		156,203
Long term investment (Note 6)		31,987		—		—		31,987
Total assets	$	684,330	$	156,203	$	—	$	840,533

Schedule of fair value of liabilities measured on recurring basis

The following fair value hierarchy table presents information about each major category of our financial liabilities measured at fair value on a recurring basis as of December 31, 2016 (in thousands):

	Fair Value Measurement at Reporting Date Using:
	Quoted Prices in		Significant Other		Significant
	Active Markets for		Observable		Unobservable
	Identical Assets		Inputs		Inputs		Balance as of
	(Level 1)		(Level 2)		(Level 3)		December 31, 2016
Contingent consideration (Note 2)	$	—	$	—	$	301,000	$	301,000
Total liabilities	$	—	$	—	$	301,000	$	301,000