Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2016

Investments Debt And Equity Securities [Abstract]

Summary of Available-for-Sale Investments

The following tables summarize our amortized cost, gross unrealized gains and losses and fair value of our available-for-sale investments in marketable securities (in thousands):

	September 30, 2016
			Gross		Gross
	Amortized		Unrealized		Unrealized		Aggregate
	Cost		Gains		Losses		Fair Value
U.S. government and government agency debt securities	$	3,000	$	1	$	—	$	3,001
Corporate debt securities		1,500		—		—		1,500
Total	$	4,500	$	1	$	—	$	4,501

	December 31, 2015
			Gross		Gross
	Amortized		Unrealized		Unrealized			Aggregate
	Cost		Gains		Losses			Fair Value
U.S. government and government agency debt securities	$	145,066	$	—	$	(80	)	$	144,986
Corporate debt securities		100,093		12		(58	)		100,047
Total	$	245,159	$	12	$	(138	)	$	245,033

Fair Value of Available-for-Sale Marketable Securities by Contractual Maturities

The estimated fair value of available-for-sale marketable securities, classified by their contractual maturities was as follows (in thousands):

	September 30, 2016
Due within one year	$	4,501
After one year through three years		—
Total	$	4,501