Accumulated Other Comprehensive Income (Loss) - Summary of Changes (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 64,510
Ending balance	37,870
Accumulated net unrealized investment gain (loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	28	$ (11)
Unrealized gain on marketable securities	(2)	65
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Net current period other comprehensive income	(2)	65
Ending balance	$ 26	$ 54