Other Comprehensive Income - Schedule of Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Net gains arising during the period, Before Tax	$ 9,993		$ 2,438	$ 20,376
Less reclassification adjustment for net gains included in net income, Before Tax	(2,587)		(32,068)	(11,598)
Net change, Unrealized gains on AFS securities, Before Tax	7,406		(29,630)	8,778
Net change in non-credit impairment losses on securities, Before Tax	15,032		(42,531)	5,301
Less reclassification adjustment for credit impairment losses included in net income, Before Tax	4,220		18,570	4,381
Net change, Non-credit impairment losses on securities available for sale and held to maturity, Before Tax	19,252		(23,961)	9,682
Net (losses) gains arising during the period, Before Tax	(5,773)		(24,393)	1,493
Less reclassification adjustment for losses included in net income, Before Tax	6,478		3,067	1,967
Net change, Unrealized gains and losses on derivatives (cash flow hedges), Before Tax	705		(21,326)	3,460
Amortization of prior service cost, Before Tax	54,571	45,487	593	885
Amortization of net loss, Before Tax	16,762		(19,812)	340
Net change, Defined benefit pension plan, Before Tax	(9,241)		(19,219)	1,225
Total other comprehensive income (loss), Before Tax	18,122		(94,136)	23,145
Net gains arising during the period, Tax Effect	(4,311)		(925)	(7,739)
Less reclassification adjustment for net gains included in net income, Tax Effect	1,042		12,394	4,268
Net change, Unrealized gains on AFS securities, Tax Effect	(3,269)		11,469	(3,471)
Net change in non-credit impairment losses on securities, Tax Effect	(5,090)		15,875	(1,973)
Less reclassification adjustment for credit impairment losses included in net income, Tax Effect	(1,771)		(6,937)	(1,640)
Net change, Non-credit impairment losses on securities available for sale and held to maturity, Tax Effect	(6,861)		8,938	(3,613)
Net (losses) gains arising during the period, Tax Effect	2,422		10,236	(627)
Less reclassification adjustment for losses included in net income, Tax Effect	(2,718)		(1,287)	(825)
Net change, Unrealized gains and losses on derivatives (cash flow hedges), Tax Effect	(296)		8,949	(1,452)
Amortization of prior service cost, Tax Effect	(556)		(245)	(367)
Amortization of net loss, Tax Effect	3,903		8,303	(145)
Net change, Defined benefit pension plan, Tax Effect	3,836		8,058	(512)
Total other comprehensive income (loss), Tax Effect	(6,590)		37,414	(9,048)
Net gains arising during the period, After Tax	5,682		1,513	12,637
Less reclassification adjustment for net gains included in net income, After Tax	(1,545)		(19,674)	(7,330)
Net change, Unrealized gains on AFS securities, After Tax	4,137		(18,161)	5,307
Net change in non-credit impairment losses on securities, After Tax	9,942		(26,656)	3,328
Less reclassification adjustment for credit impairment losses included in net income, After Tax	2,449		11,633	2,741
Net change, Non-credit impairment losses on securities available for sale and held to maturity, After Tax	12,391		(15,023)	6,069
Net (losses) gains arising during the period, After Tax	(3,351)		(14,157)	866
Less reclassification adjustment for losses included in net income, After Tax	3,760		1,780	1,142
Net change, Unrealized gains and losses on derivatives (cash flow hedges), After Tax	409		(12,377)	2,008
Amortization of prior service cost, After Tax	38		(348)	518
Amortization of net loss, After Tax	(5,443)		(11,509)	195
Net change, Defined benefit pension plan, After Tax	(5,405)		(11,161)	713
Total other comprehensive income (loss), After Tax	$ 11,532		$ (56,722)	$ 14,097