Consolidated Statement of Comprehensive Income (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	$ 26,363	$ 40,982	$ 75,279	$ 140,473
Unrealized gains and losses on securities:
Change in unrealized securities gains (losses) arising during period	(11,444)	3,470	32,006	(36,998)
Tax effect	4,444	(1,177)	(12,425)	14,657
Total change in unrealized gains and losses on securities, net of tax	(7,000)	2,293	19,581	(22,341)
Change in fair value of cash flow hedges:
Change in unrecognized loss on cash flow hedges	949	287	2,236	2,489
Tax effect	(367)	(186)	(863)	(1,055)
Total change in unrecognized loss on cash flow hedges, net of tax	582	101	1,373	1,434
Change in pension obligation:
Reclassification adjustment for gains included in income before income taxes	822	4,298	4,019	12,896
Tax effect	(319)	(2,061)	(1,563)	(5,428)
Total change in pension obligation, net of tax	503	2,237	2,456	7,468
Net current period other comprehensive (loss) income	(5,915)	4,631	23,410	(13,439)
Total comprehensive income	$ 20,448	$ 45,613	$ 98,689	$ 127,034