Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2015

Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table presents our fair value hierarchy for assets and liabilities measured at fair value on a recurring basis as of December 31, 2015 and December 31, 2014 (in thousands):



	Fair value as of December 31, 2015
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents	$	15,152	$	15,152	$	—	$	—
Corporate debt securities	80,967		—		80,967		—
Certificates of deposit	13,640		—		13,640		—
Commercial paper	3,496		—		3,496		—
	$	113,255	$	15,152	$	98,103	$	—



	Fair value as of December 31, 2014
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents	$	37,072	$	37,072	$	—	$	—
Corporate debt securities	104,920		—		104,920		—
Certificates of deposit	14,600		—		14,600		—
Commercial paper	2,896		—		2,896		—
	$	159,488	$	37,072	$	122,416	$	—
Liabilities:
Convertible note payable	$	23,397	$	—	$	—	$	23,397

Reconciliation of Liabilities Measured at Fair Value on Quarterly Basis

The following table presents a reconciliation of the liability measured at fair value using significant unobservable inputs (Level 3) from December 31, 2014 to December 31, 2015 (in thousands):



	Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Balance at December 31, 2014	$	23,397
Change in estimated fair value of convertible note payable	1,811
Convertible note converted to shares of common stock	(25,208		)
Balance at December 31, 2015	$	—