Other Comprehensive Income (Loss) - Component of Other Comprehensive Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Before Tax Amount	$ (21,344)	$ 1,882
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Before Tax Amount	(8,459)
Securities available for sale and transferred securities, Reclassification adjustment for (gains) losses included in net income, Before Tax Amount	(5)	491
Total securities available for sale and transferred securities, Before Tax Amount	(29,808)	2,373
Defined-benefit post-retirement benefit plans, Change in the net actuarial gain/loss, Before Tax Amount	1,640	1,229
Derivatives, Change in the accumulated gain/loss on effective cash flow hedge derivatives, Before Tax Amount		(427)
Derivatives, Reclassification adjustments for (gains) losses included in net income, Interest rate swaps on variable-rate loans, Before Tax Amount	(9,345)	(9,345)
Derivatives, Reclassification adjustments for (gains) losses included in net income, Interest rate swap on junior subordinated deferrable interest debentures, Before Tax Amount	1,085	1,033
Total derivatives, Before Tax Amount	(8,260)	(8,739)
Total other comprehensive income, Before Tax Amount	(36,428)	(5,137)
Securities available for sale and transferred securities, Change in net unrealized gain/loss during the period, Tax Expense (Benefit)	(7,470)	658
Securities available for sale and transferred securities, Change in net unrealized gain on securities transferred to held to maturity, Tax Expense (Benefit)	(2,961)
Securities available for sale and transferred securities, Reclassification adjustment for net (gains) losses included in net income, Tax Expense (Benefit)	(2)	172
Total securities available for sale and transferred securities, Tax Expense (Benefit)	(10,433)	830
Defined-benefit post-retirement benefit plans, Change in the net actuarial gain/loss, Tax Expense (Benefit)	574	430
Derivatives, Change in the accumulated gain/loss on effective cash flow hedge derivatives, Tax Expense (Benefit)		(150)
Derivatives, Reclassification adjustments for (gains) losses included in net income, Interest rate swaps on variable-rate loans, Tax Expense (Benefit)	(3,271)	(3,271)
Derivatives, Reclassification adjustments for (gains) losses included in net income, Interest rate swap on junior subordinated deferrable interest debentures, Tax Expense (Benefit)	380	362
Total derivatives, Tax Expense (Benefit)	(2,891)	(3,059)
Total other comprehensive income, Tax Expense (Benefit)	(12,750)	(1,799)
Change in net unrealized gain/loss during the period, Net of Tax	(13,874)	1,224
Change in net unrealized gain on securities transferred to held to maturity, Net of Tax	(5,498)
Reclassification adjustment for net (gains) losses included in net income, Net of Tax	(3)	319
Total securities available for sale	(19,375)	1,543
Change in the net actuarial gain/loss, Net of Tax	1,066	799
Change in the accumulated gain/loss on effective cash flow hedge derivatives, Net of Tax		(277)
Interest rate swaps on variable-rate loans, Net of Tax	(6,074)	(6,074)
Interest rate swap on junior subordinated deferrable interest debentures, Net of Tax	705	671
Total derivatives, Net of Tax	(5,369)	(5,680)
Other comprehensive income (loss), net of tax	$ (23,678)	$ (3,338)