Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 46,553	$ 33,202	$ 135,630	$ 128,640
Other comprehensive income:
Net change in unrealized (losses) gains	(6,293)	(9,685)	9,119	(96,074)
Reclassification adjustment for net (gains) losses realized and included in earnings	(6)	1,553	2,195	5,835
Amortization of unrealized net gain (loss) on securities transferred to held to maturity	892	(1,456)	2,463	(7,099)
Other comprehensive (expense) income, before income taxes	(5,407)	(9,588)	13,777	(97,338)
Income tax (benefit) expense	(2,005)	(3,512)	5,091	(35,492)
Other comprehensive (loss) income net of income taxes	(3,402)	(6,076)	8,686	(61,846)
Comprehensive income	$ 43,151	$ 27,126	$ 144,316	$ 66,794