Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Amortization of prior service cost									$ (7,104)	$ (7,338)	$ (6,018)
Interest and dividends on investment									461	1,027	1,398
Interest expense	(40,787)	(42,110)	(42,483)	(42,997)	(44,440)	(45,408)	(44,787)	(46,677)	(168,377)	(181,312)	(199,013)
Amortization of net actuarial loss									(13,003)	14,326
Recognition of loss due to curtailment									(12,981)
Total before tax									42,364	(9,241)	(19,219)
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect	(16,061)	(7,143)	(10,961)	(12,814)	(14,702)	(22,402)	(14,366)	(15,278)	(46,979)	(66,748)	(62,706)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Out Of Accumulated Other Comprehensive Loss [LineItems]
Interest expense									(6,898)	(6,478)	(3,067)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax									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									14,678
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect									(6,156)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax									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									461
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect									(193)
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax									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									(6,898)
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect									2,893
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax									(4,005)
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									(2,440)
Amortization of net actuarial loss									(1,970)
Recognition of loss due to curtailment									(750)
Total before tax									(5,160)
Amounts Reclassified from Accumulated Other Comprehensive Loss, tax effect									2,093
Amounts Reclassified from Accumulated Other Comprehensive Loss, net of tax									$ (3,067)