Cash, Cash Equivalents and Available for Sale Securities - Schedule of Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (94,618)	$ 59,947	$ 128,537	$ 169,720
Current period changes in fair value before reclassifications, net of tax	261	(351)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0	(57)
Other comprehensive income (loss)	261	(408)	(65)
Ending balance	(94,618)	59,947	128,537
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(212)	(473)	(65)	$ 0
Ending balance	$ (212)	$ (473)	$ (65)