Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value Hierarchy

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

	Fair Value at December 31, 2018						Fair Value at December 31, 2017
		Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
Assets
Money market funds(1)	$	39,168	$	―	$	―	$	36,762	$	―	$	―
Asset-backed securities(2)		―		19,997		―		―		29,750		―
Corporate debt securities(3)		―		26,219		―		―		80,309		―
Total cash equivalents and marketable securities	$	39,168	$	46,216	$	―	$	36,762	$	110,059	$	―
Liabilities
Convertible notes payable	$	―	$	197,935	$	―	$	―	$	152,396	$	―

(1)	Classified as cash and cash equivalents as of December 31, 2018 and 2017, respectively (see Note 3).
(2)	Includes $15,000 and $16,007 classified as cash and cash equivalents as of December 31, 2018 and 2017, respectively, on the consolidated balance sheets.
(3)	Includes $9,236 and $43,056 classified as cash and cash equivalents as of December 31, 2018 and 2017, respectively, on the consolidated balance sheets.