Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ 394,498
Other comprehensive income before reclassifications			7,869
Amounts reclassified from accumulated other comprehensive income			(8,985)
Other comprehensive income (loss)	$ 2,591	$ (16,360)	(1,116)	$ (16,059)
Ending balance	406,922		406,922
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			37,858
Ending balance	36,742		36,742
Foreign Currency [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(1,066)
Other comprehensive income before reclassifications			398
Amounts reclassified from accumulated other comprehensive income			0
Other comprehensive income (loss)			398
Ending balance	(668)		(668)
Unrealized Holding Gains on Available-for-sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			38,924
Other comprehensive income before reclassifications			7,471
Amounts reclassified from accumulated other comprehensive income			(8,985)
Other comprehensive income (loss)			(1,514)
Ending balance	$ 37,410		$ 37,410