Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2015

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 September 30, 2015 and December 31, 2014:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
September 30, 2015
Corporate bonds	$	131,740	$	6	$	(116	)	$	131,630
Municipal bonds	17,957		14		(1		)	17,970
Commercial paper	36,118		—		—			36,118
Agency securities	7,279		7		—			7,286
Certificates of deposit	2,492		—		—			2,492
Government securities	1,199		2		—			1,201
Total marketable securities	$	196,785	$	29	$	(117	)	$	196,697
December 31, 2014
Corporate bonds	$	99,592	$	1	$	(119	)	$	99,474
Municipal bonds	18,146		1		(10		)	18,137
Commercial paper	9,196		—		—			9,196
Certificates of deposit	498		—		—			498
Total marketable securities	$	127,432	$	2	$	(129	)	$	127,305

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 September 30, 2015 and December 31, 2014, by maturity:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
September 30, 2015
Due in one year or less	$	147,745	$	13	$	(75	)	$	147,683
Due after one year	49,040		16		(42		)	49,014
Total marketable securities	$	196,785	$	29	$	(117	)	$	196,697
December 31, 2014
Due in one year or less	$	127,029	$	2	$	(129	)	$	126,902
Due after one year	403		—		—			403
Total marketable securities	$	127,432	$	2	$	(129	)	$	127,305