Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Foreign currency translation adjustments:
Change in unrealized foreign currency translation gains (losses) before income tax expense (benefit)	$ 6,753	$ (1,167)	$ 7,880	$ 14,869
Income tax expense (benefit) on unrealized foreign currency translation gains (losses)	74	(10)	88	159
Change in unrealized foreign currency translation gains (losses), net of income taxes	6,679	(1,157)	7,792	14,710
Unrealized gain (losses) on available-for-sale securities:
Change in unrealized holding gains (losses) on investment securities	3,889	33,568	11,170	58,284
Change in net unrealized investment gains (losses) not-other-than-temporarily impaired, income tax expense (benefit)	1,361	11,749	3,910	20,398
Change in unrealized holding gains (losses) on available-for-sale securities arising during period, net of income taxes	2,528	21,819	7,260	37,886
Reclassification adjustment for realized investment (gains) losses included in net income	(273)	(3,219)	(341)	(2,332)
Income tax (expense) benefits on (gains) losses reclassified from accumulated OCI to net income	(96)	(1,127)	(119)	(816)
Reclassification from accumulated OCI to net income for (gains) losses realized on available-for-sale securities, net of income taxes	(177)	(2,092)	(222)	(1,516)
Change in unrealized gains (losses) on available-for-sale securities, net of income taxes and reclassification adjustment	$ 2,351	$ 19,727	$ 7,038	$ 36,370