Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2015

Marketable Securities

Summary of marketable securities portfolio

			Net		Net
	Amortized		Unrealized		Unrealized		Estimated
	Cost		Gains		Losses		Fair Value
	(in thousands)
December 31, 2015
Corporate debt securities	$	187,153	$	—	$	(809)	$	186,344
December 31, 2014
Corporate debt securities	$	144,684	$	—	$	(282)	$	144,402
Mortgage backed securities		1,461		2,103		—		3,564
	$	146,145	$	2,103	$	(282)	$	147,966

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 and liabilities measured at fair value on a recurring basis as of December 31, 2015 (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, 2015
Cash and cash equivalents	$	521,439	$	—	$	—	$	521,439
Corporate debt securities		—		186,344		—		186,344
Long term investment (Note 5)		35,248		—		—		35,248
Total assets	$	556,687	$	186,344	$	—	$	743,031

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, 2014 (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, 2014
Cash and cash equivalents	$	452,297	$	—	$	—	$	452,297
Corporate debt securities		—		144,402		—		144,402
Mortgage-backed securities		—		3,564		—		3,564
Total assets	$	452,297	$	147,966	$	—	$	600,263