Consolidated Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 63,816	$ 22,479
Unrealized gains and losses on securities:
Change in unrealized securities gains (losses) arising during period	30,415	11,899
Tax effect	(11,813)	(4,643)
Reclassification adjustment for gains included in income before income taxes	5,126	0
Tax effect	1,977	0
Total change in unrealized gains and losses on securities, net of tax	15,453	7,256
Change in fair value of cash flow hedges:
Change in unrecognized loss on cash flow hedges	576	719
Tax effect	(222)	(278)
Total change in unrecognized loss on cash flow hedges, net of tax	354	441
Change in pension obligation:
Reclassification adjustment for losses included in income before income taxes	2,886	1,599
Tax effect	(1,123)	(622)
Total change in pension obligation, net of tax	1,763	977
Net current period other comprehensive income	17,570	8,674
Total comprehensive income	$ 81,386	$ 31,153