Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2016

Summary of financial assets and liabilities measured on recurring basis

	September 30, 2016								December 31, 2015
	Level I		Level II		Level III		Total		Level I		Level II		Level III		Total
	(in thousands)
Financial Assets:
Money market deposits	$	9,811	$	—	$	—	$	9,811	$	5,966	$	—	$	—	$	5,966
U.S. Treasury securities		75,565		—		—		75,565		103,813		—		—		103,813
U.S. agency securities		—		64,469		—		64,469		—		78,853		—		78,853
Municipal securities		—		17,683		—		17,683		—		18,920		—		18,920
Total financial assets	$	85,376	$	82,152	$	—	$	167,528	$	109,779	$	97,773	$	—	$	207,552
Current Liabilities:
Warrants	$	—	$	—	$	3,558	$	3,558	$	—	$	—	$	3,649	$	3,649
Total financial liabilities	$	—	$	—	$	3,558	$	3,558	$	—	$	—	$	3,649	$	3,649

Warrants

Rollforward of fair value determined by Level 3 inputs

	Warrants
	(in thousands)
Balance at December 31, 2015	$	3,649
Change in fair value		(91)
Balance at September 30, 2016	$	3,558