Amount of gain (loss) related to change in benefit obligation resulting from changes in actuarial assumptions, for example, but not limited to, interest, mortality, employee turnover, salary, and temporary deviation from the substantive plan.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Gain or Loss

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The amount of decrease that is related to an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Glossary Plan Curtailment

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-Subparagraph (a)(2)

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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-SubTopic 20

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-Paragraph 1

-Subparagraph (h)(1)

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-Glossary Service Cost (Component of Net Periodic Pension Cost)

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-Section 50

-Paragraph 1

-Subparagraph (a)(1)

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This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting.

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Article 5

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-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph ((b)(7))

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h))

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-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Article 4

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-Glossary Income Tax Expense (or Benefit)

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-Topic 740

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (a),(b)

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Amount of the cost of borrowed funds accounted for as interest expense.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

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-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.9)

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-Number 210

-Section 04

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-Article 9

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 45

-Paragraph 11

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Amount before tax, after reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to pension and other postretirement defined benefit plans.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 10A

-Subparagraph (i-k)

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This item represents reductions in the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held due to increases in cash flows expected to be collected and recognized over the remaining life of the security.

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Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Interest and dividends on investment									$ 661	$ 461	$ 1,027
Interest expense	(42,296)us-gaap_InterestExpense	(40,791)us-gaap_InterestExpense	(39,745)us-gaap_InterestExpense	(39,014)us-gaap_InterestExpense	(40,787)us-gaap_InterestExpense	(42,110)us-gaap_InterestExpense	(42,483)us-gaap_InterestExpense	(42,997)us-gaap_InterestExpense	(161,846)us-gaap_InterestExpense	(168,377)us-gaap_InterestExpense	(181,312)us-gaap_InterestExpense
Amortization of prior service cost									0us-gaap_DefinedBenefitPlanServiceCost	(7,104)us-gaap_DefinedBenefitPlanServiceCost	(7,338)us-gaap_DefinedBenefitPlanServiceCost
Amortization of net actuarial loss									(28,749)	13,003
Recognition of loss due to curtailment									0us-gaap_DefinedBenefitPlanCurtailments	(12,981)us-gaap_DefinedBenefitPlanCurtailments
Income before income taxes	32,962	38,336	41,271	34,665	55,669	34,264	44,883	44,124	147,234	178,940	210,375
Net change, Defined benefit pension plan, Before Tax									(27,371)	42,364	(9,241)
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect	(7,827)us-gaap_IncomeTaxExpenseBenefit	(10,654)us-gaap_IncomeTaxExpenseBenefit	(11,751)us-gaap_IncomeTaxExpenseBenefit	(830)us-gaap_IncomeTaxExpenseBenefit	(16,061)us-gaap_IncomeTaxExpenseBenefit	(7,143)us-gaap_IncomeTaxExpenseBenefit	(10,961)us-gaap_IncomeTaxExpenseBenefit	(12,814)us-gaap_IncomeTaxExpenseBenefit	(31,062)us-gaap_IncomeTaxExpenseBenefit	(46,979)us-gaap_IncomeTaxExpenseBenefit	(66,748)us-gaap_IncomeTaxExpenseBenefit
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Interest expense									(6,663)	(6,898)	(6,478)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax									(3,379)	1,718
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] \| Unrealized Gains and Losses on AFS Securities [Member]
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Gains on securities transactions, net									745	14,678
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect									(312)	(6,156)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax									433	8,522
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] \| Non-Credit Impairment Losses on Securities [Member]
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Interest and dividends on investment									661	461
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect									(278)	(193)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax									383	268
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] \| Unrealized Losses on Derivatives (Cash Flow Hedges) Before Tax [Member]
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Interest expense									(6,663)	(6,898)
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect									2,777	2,893
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax									(3,886)	(4,005)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] \| Defined Benefit Pension Plan [Member]
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Amortization of prior service cost									(305)	(2,440)
Amortization of net actuarial loss									(226)	(1,970)
Recognition of loss due to curtailment									0	(750)
Income before income taxes									(531)	(5,160)
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect									222	2,093
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax									$ (309)	$ (3,067)