Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 404,345
Other comprehensive income before reclassifications	6,055
Amounts reclassified from accumulated other comprehensive income	(655)
Other comprehensive income (loss)	5,400	$ (7,631)
Ending balance	412,902
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	33,220
Ending balance	38,620
Foreign Currency [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(831)
Other comprehensive income before reclassifications	65
Amounts reclassified from accumulated other comprehensive income	0
Other comprehensive income (loss)	65
Ending balance	(766)
Unrealized Holding Gains on Available-for-sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	34,051
Other comprehensive income before reclassifications	5,990
Amounts reclassified from accumulated other comprehensive income	(655)
Other comprehensive income (loss)	5,335
Ending balance	$ 39,386