Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 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):

	March 31, 2016
	Level I		Level II		Level III		Total
Financial Assets:
Money market funds	$	552,590	$	—	$	—	$	552,590
Money market funds-restricted	4,041		—		—		4,041
U.S. government notes	9,091		—		—		9,091
Corporate bonds	—		42,498		—		42,498
Total financial assets	$	565,722	$	42,498	$	—	$	608,220

	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