Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Changes in Accumulated Other Comprehensive Income by Component [Roll Forward]
Beginning balance			$ 399,496
Other comprehensive income (loss)	$ (16,360)	$ (5,295)	(16,059)	$ 4,875
Ending balance	392,885		392,885
AOCI Attributable to Parent [Member]
Changes in Accumulated Other Comprehensive Income by Component [Roll Forward]
Beginning balance			52,230
Other comprehensive income before reclassifications			(14,401)
Amounts reclassified from accumulated other comprehensive income			(1,658)
Other comprehensive income (loss)			(16,059)
Ending balance	36,171		36,171
Foreign Currency [Member]
Changes in Accumulated Other Comprehensive Income by Component [Roll Forward]
Beginning balance			390
Other comprehensive income before reclassifications			(1,102)
Amounts reclassified from accumulated other comprehensive income			0
Other comprehensive income (loss)			(1,102)
Ending balance	(712)		(712)
Unrealized Holding Gains on Available-for-sale Securities [Member]
Changes in Accumulated Other Comprehensive Income by Component [Roll Forward]
Beginning balance			51,840
Other comprehensive income before reclassifications			(13,299)
Amounts reclassified from accumulated other comprehensive income			(1,658)
Other comprehensive income (loss)			(14,957)
Ending balance	$ 36,883		$ 36,883