Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 151,398	$ 137,210	$ 111,196
Unrealized gains (losses) on securities
Before tax	72,488	(102,790)	8,793
Tax effect	(28,660)	40,608	(3,332)
Net of tax	43,828	(62,182)	5,461
Before tax	(504)	(3,000)	4,895
Tax effect	200	1,193	(1,940)
Net of tax	(304)	(1,807)	2,955
Net unrealized gains (losses) on securities	44,132	(60,375)	2,506
Unrealized (losses) gains on derivative instruments
Before tax	(91)	4,702	2,960
Tax effect	36	(1,872)	(1,170)
Net unrealized (losses) gains on derivative instruments	(55)	2,830	1,790
Foreign currency translation adjustment
Before tax	(24,346)	(17,564)	8,249
Tax effect	5,973	4,362	(1,956)
Net foreign currency translation adjustment	(18,373)	(13,202)	6,293
Total other comprehensive income (loss)	25,704	(70,747)	10,589
Comprehensive income	$ 177,102	$ 66,463	$ 121,785