Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 44,522	$ 26,686	$ 111,680	$ 49,165
Unrealized gains and losses on securities:
Change in unrealized securities gains (losses) arising during period	(29,226)	31,550	1,189	43,449
Tax effect	11,352	(12,225)	(461)	(16,868)
Reclassification adjustment for net gains realized and included in income before income taxes	147	0	5,273	0
Tax effect	74	0	2,051	0
Total change in unrealized gains and losses on securities, net of tax	(17,947)	19,325	(2,494)	26,581
Change in fair value of cash flow hedges:
Change in unrecognized loss on cash flow hedges	709	568	1,285	1,287
Tax effect	(274)	(218)	(496)	(496)
Total change in unrecognized loss on cash flow hedges, net of tax	435	350	789	791
Change in pension obligation:
Reclassification adjustment for losses included in income before income taxes	2,887	1,598	5,773	3,197
Tax effect	(1,123)	(622)	(2,246)	(1,244)
Total change in pension obligation, net of tax	1,764	976	3,527	1,953
Net current period other comprehensive income	(15,748)	20,651	1,822	29,325
Total comprehensive income	$ 28,774	$ 47,337	$ 113,502	$ 78,490