Consolidated Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 22,366	$ 55,585
Unrealized gains on securities:
Change in unrealized securities gains arising during period	11,899	(1,476)
Tax effect	(4,643)	565
Total change in unrealized gains on securities, net of tax	7,256	(911)
Change in fair value of cash flow hedges:
Change in unrecognized loss on cash flow hedges	719	815
Tax effect	(278)	(322)
Total change in unrecognized loss on cash flow hedges, net of tax	441	493
Change in pension obligation:
Reclassification adjustment for losses included in income before income taxes	1,599	4,304
Tax effect	(622)	(1,685)
Total change in pension obligation, net of tax	977	2,619
Net current period other comprehensive income	8,674	2,201
Total comprehensive income	$ 31,040	$ 57,786