Available for Sale Securities (Tables)

6 Months Ended

Jun. 30, 2017

Investments Debt And Equity Securities [Abstract]

Summary of Available for Sale Securities at Fair Value

Available for sale securities at June 30, 2017 and December 31, 2016 consist of the following:

			Gross		Gross
			Unrealized		Unrealized
	Amortized Cost		Gains		Losses			Fair Value
	(in thousands)
June 30, 2017
Cash and cash equivalents	$	125,390	$	—	$	—		$	125,390
Available for sale securities:
Certificates of deposit	$	14,855	—		—			$	14,855
U.S. Government debt securities		128,413	—			(187	)		128,226
Corporate debt securities		52,810				(66	)		52,744
Total available for sale securities	$	196,078	$	—	$	(253	)	$	195,825
Total cash, cash equivalents, and available for sale securities	$	321,468	$	—	$	(253	)	$	321,215

			Gross		Gross
			Unrealized		Unrealized
	Amortized Cost		Gains		Losses			Fair Value
	(in thousands)
December 31, 2016
Cash and cash equivalents	$	187,335	$	—	$	—		$	187,335
Available for sale securities:
Certificates of deposit	$	12,698	—			—		$	12,698
U.S. Government debt securities		50,952	—			(32	)		50,920
Corporate debt securities		9,398	—			(8	)		9,390
Total available for sale securities	$	73,048	$	—	$	(40	)	$	73,008
Total cash, cash equivalents, and available for sale securities	$	260,383	$	—	$	(40	)	$	260,343

Estimated Fair Value of Available for Sale Securities by Contractual Maturity

The estimated fair value of the Company’s available for sale securities balance at June 30, 2017, by contractual maturity, is as follows:

Due in one year or less	$	191,182
Due after one year		4,643
Total available for sale securities	$	195,825