Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (24,244)	$ 48,603	$ 65,602
Other Comprehensive Income (Loss) Before Reclassifications	30,610	(122,403)	(29,050)
Amounts reclassified from accumulated other comprehensive income (loss)	913	3,852	1,008
Income tax (expense) benefit	(12,129)us-gaap_OtherComprehensiveIncomeLossTax	45,704us-gaap_OtherComprehensiveIncomeLossTax	11,043us-gaap_OtherComprehensiveIncomeLossTax
Net other comprehensive income (loss) during period	19,394	(72,847)	(16,999)
Ending Balance	(4,850)	(24,244)	48,603
Investment Securities Available For Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(11,396)	86,109	99,761
Other Comprehensive Income (Loss) Before Reclassifications	49,038	(158,207)	(19,042)
Amounts reclassified from accumulated other comprehensive income (loss)	(494)	(564)	(4,261)
Income tax (expense) benefit	(18,636)	61,266	9,651
Net other comprehensive income (loss) during period	29,908	(97,505)	(13,652)
Ending Balance	18,512	(11,396)	86,109
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(12,848)	(37,506)	(33,173)
Other Comprehensive Income (Loss) Before Reclassifications	(18,428)	35,804	(10,014)
Amounts reclassified from accumulated other comprehensive income (loss)	1,407	4,416	3,315
Income tax (expense) benefit	6,507	(15,562)	2,366
Net other comprehensive income (loss) during period	(10,514)	24,658	(4,333)
Ending Balance	(23,362)	(12,848)	(37,506)
Cash Flow Hedging Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	0	0	(986)
Other Comprehensive Income (Loss) Before Reclassifications	0	0	6
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	1,954
Income tax (expense) benefit	0	0	(974)
Net other comprehensive income (loss) during period	0	0	986
Ending Balance	$ 0	$ 0	$ 0

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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Amount before tax and reclassification adjustments of other comprehensive income (loss).

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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Amount before tax of reclassification adjustments of other comprehensive income (loss).

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