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, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Interest and dividends on investment	$ 110	$ 75	$ 308	$ 188
Interest expense	(39,745)	(42,483)	(78,759)	(85,480)
Amortization of prior service cost	0	(2,056)	0	(4,043)
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect	(11,751)	(10,961)	(12,581)	(23,775)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Interest expense	(1,664)	(1,714)	(3,312)	(3,594)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	(942)	(1,999)	(1,834)	(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 on securities transactions, net	7	41	(1)	3,999
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect	(3)	(16)	0	(1,675)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	4	25	(1)	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	110	75	308	188
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect	(46)	(32)	(129)	(79)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	64	43	179	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	(1,664)	(1,714)	(3,312)	(3,594)
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect	691	719	1,374	1,508
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	(973)	(995)	(1,938)	(2,086)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] | Defined Benefit Pension Plans [Member]
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Amortization of prior service cost	0	(241)	0	(443)
Amortization of net actuarial loss	(62)	(811)	(124)	(1,605)
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	0	(750)	0	(750)
Total before tax	(62)	(1,802)	(124)	(2,798)
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect	25	730	50	1,133
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax	$ (37)	$ (1,072)	$ (74)	$ (1,665)