Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

Fair value of financial assets by level

The following table sets forth the fair value of our financial assets by level within the fair value hierarchy (in thousands):

	September 30, 2016
	Level I		Level II		Level III		Total
Financial Assets:
Money market funds	$	304,926	$	—	$	—	$	304,926
Money market funds-restricted	4,041		—		—		4,041
Commercial Paper	11,997		—		—		11,997
U.S. government notes	139,499		—		—		139,499
Corporate bonds	—		148,171		—		148,171
Total financial assets	$	460,463	$	148,171	$	—	$	608,634

	December 31, 2015
	Level I		Level II		Level III		Total
Financial Assets:
Money market funds	$	104,156	$	—	$	—	$	104,156
Money market funds-restricted	4,041		—		—		4,041
Total financial assets	$	108,197	$	—	$	—	$	108,197