Accumulated Other Comprehensive Income (Loss) Reclassifications Out of AOCI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (25,015)	$ 66,579	$ 48,603	$ 65,602
Other comprehensive income (loss) before reclassification	(20,558)	3,499	(142,318)	2,876
Amounts reclassified from accumulated other comprehensive income (loss)	842	(2,310)	2,688	(55)
Income tax (expense) benefit	7,611	(465)	53,907	(1,120)
Net other comprehensive income (loss) during period	(12,105)	724	(85,723)	1,701
Ending Balance	(37,120)	67,303	(37,120)	67,303
Securities Available For Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	11,153	99,021	86,109	99,761
Other comprehensive income (loss) before reclassification	(20,558)	3,479	(142,318)	2,870
Amounts reclassified from accumulated other comprehensive income (loss)	(248)	(3,506)	(582)	(4,109)
Income tax (expense) benefit	8,031	11	55,169	483
Net other comprehensive income (loss) during period	(12,775)	(16)	(87,731)	(756)
Ending Balance	(1,622)	99,005	(1,622)	99,005
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(36,168)	(32,319)	(37,506)	(33,173)
Other comprehensive income (loss) before reclassification	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	1,090	700	3,270	2,100
Income tax (expense) benefit	(420)	(273)	(1,262)	(819)
Net other comprehensive income (loss) during period	670	427	2,008	1,281
Ending Balance	(35,498)	(31,892)	(35,498)	(31,892)
Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	0	(123)	0	(986)
Other comprehensive income (loss) before reclassification	0	20	0	6
Amounts reclassified from accumulated other comprehensive income (loss)	0	496	0	1,954
Income tax (expense) benefit	0	(203)	0	(784)
Net other comprehensive income (loss) during period	0	313	0	1,176
Ending Balance	$ 0	$ 190	$ 0	$ 190