Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Summary of Marketable Securities Designated as Available-for-Sale

The following is a summary of marketable securities designated as available-for-sale as of March 31, 2016 and December 31, 2015:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
March 31, 2016
Corporate bonds	$	115,144	$	14	$	(90	)	$	115,068
Municipal bonds	13,130		—		(6		)	13,124
Government securities	11,693		12		(2		)	11,703
Commercial paper	7,473		—		—			7,473
Agency securities	7,267		—		(1		)	7,266
Certificates of deposit	2,244		—		—			2,244
Total marketable securities	$	156,951	$	26	$	(99	)	$	156,878
December 31, 2015
Corporate bonds	$	125,132	$	1	$	(304	)	$	124,829
Commercial paper	37,236		—		—			37,236
Municipal bonds	16,228		2		(6		)	16,224
Government securities	8,704		1		(17		)	8,688
Agency securities	7,273		—		(20		)	7,253
Certificates of deposit	2,244		—		—			2,244
Total marketable securities	$	196,817	$	4	$	(347	)	$	196,474

Summary of Amortized Cost and Estimated Fair Value of Marketable Securities by Maturity

The following is a summary of amortized cost and estimated fair value of marketable securities as of March 31, 2016 and December 31, 2015, by maturity:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
March 31, 2016
Due in one year or less	$	145,592	$	18	$	(89	)	$	145,521
Due after one year	11,359		8		(10		)	11,357
Total marketable securities	$	156,951	$	26	$	(99	)	$	156,878
December 31, 2015
Due in one year or less	$	164,147	$	2	$	(221	)	$	163,928
Due after one year	32,670		2		(126		)	32,546
Total marketable securities	$	196,817	$	4	$	(347	)	$	196,474