Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2016

Fair Value Measurements [Abstract]

Fair Value Hierarchy

The following table represents the Company’s fair value hierarchy for its financial assets and liabilities measured at fair value (in thousands):

	Fair Value at June 30, 2016						Fair Value at December 31, 2015
Assets	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
Money market funds	$	57,086	$	—	$	—	$	14,950	$	—	$	—
U.S. Treasury securities		—		21,694		—		—		—		—
Debt securities of U.S. government agencies		—		22,537		—		—		—		—
Government-backed security		—		22,000		—		—		20,000		—
Asset-backed securities		—		55,463		—		—		28,924		—
Corporate debt securities		—		177,273		—		—		137,213		—
Total assets	$	57,086	$	298,967	$	—	$	14,950	$	186,137	$	—
Liabilities
Convertible notes payable	$	—	$	411,255	$	—	$	—	$	—	$	—