Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Interest and dividends on investment securities (taxable)	$ 75	$ 66	$ 188	$ 369
Interest expense	(42,483)	(44,787)	(85,480)	(91,464)
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect	(10,961)	(14,366)	(23,775)	(29,644)
Defined benefit pension plan:
Amortization of prior service cost	(2,056)	(1,985)	(4,043)	(3,971)
Tax effect	(10,961)	(14,366)	(23,775)	(29,644)
Reclassification out of accumulated other comprehensive income (loss) [Member]
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Interest expense	(1,714)	(1,398)	(3,594)	(2,790)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	(1,999)		(1,318)
Defined benefit pension plan:
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	(1,999)		(1,318)
Reclassification out of accumulated other comprehensive income (loss) [Member] | Unrealized Gains and Losses on Available for Sale (AFS) Securities [Member]
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Gains (losses) on securities transactions, net	41		3,999
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect	(16)		(1,675)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	25		2,324
Defined benefit pension plan:
Tax effect	(16)		(1,675)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	25		2,324
Reclassification out of accumulated other comprehensive income (loss) [Member] | Non-credit Impairment Losses on AFS Securities [Member]
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Interest and dividends on investment securities (taxable)	75		188
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect	(32)		(79)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	43		109
Defined benefit pension plan:
Tax effect	(32)		(79)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	43		109
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	(1,714)		(3,594)
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect	719		1,508
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	(995)		(2,086)
Defined benefit pension plan:
Tax effect	719		1,508
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	(995)		(2,086)
Reclassification out of accumulated other comprehensive income (loss) [Member] | Defined Benefit Pension Plans [Member]
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect	730		1,133
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	(1,072)		(1,665)
Defined benefit pension plan:
Amortization of prior service cost	(241)		(443)
Amortization of net actuarial loss	(811)		(1,605)
Recognition of loss due to curtailment	(750)		(750)
Total before tax	(1,802)		(2,798)
Tax effect	730		1,133
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	$ (1,072)		$ (1,665)