Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2016

Fair Value Measurements

Assets and liabilities measured at fair value on a recurring basis

Assets and liabilities measured at fair value on a recurring basis as of June 30, 2016 and December 31, 2015 are as follows:

			Quoted Prices		Significant
			in Active		Other		Significant
			Markets for		Observable		Unobservable
			Identical Assets		Inputs		Inputs
Assets	Total		(Level 1)		(Level 2)		(Level 3)
June 30, 2016	(in thousands)
Money market funds included in cash and cash equivalents	$	65,463	$	65,463	$	—	$	—
Marketable securities:
U.S. Treasury notes		110,019		110,019		—		—
U.S. Government agency securities		26,942		—		26,942		—
Total	$	202,424	$	175,482	$	26,942	$	—
December 31, 2015
Money market funds included in cash and cash equivalents	$	29,601	$	29,601	$	—	$	—
Marketable securities:
U.S. Treasury notes		157,981		157,981		—		—
U.S. Government agency securities		35,055		—		35,055		—
Total	$	222,637	$	187,582	$	35,055	$	—