Other Comprehensive Income - Schedule of Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement Of Stockholders Equity [Abstract]
Net gains (losses) arising during the period, Before Tax	$ (22,679)	$ 9,993	$ 2,438
Less reclassification adjustment for net gains included in net income, Before Tax	(14,678)	(2,587)	(32,068)
Net change, Unrealized gains on AFS securities, Before Tax	(37,357)	7,406	(29,630)
Net change in non-credit impairment losses on securities, Before Tax	6,266	15,032	(42,531)
Less reclassification adjustment for credit impairment losses included in net income, Before Tax	(461)	4,220	18,570
Net change, Non-credit impairment losses on securities available for sale and held to maturity, Before Tax	5,805	19,252	(23,961)
Net gains (losses) gains arising during the period, Before Tax	4,255	(5,773)	(24,393)
Less reclassification adjustment for losses included in net income, Before Tax	6,898	6,478	3,067
Net change, Unrealized gains and losses on derivatives (cash flow hedges), Before Tax	11,153	705	(21,326)
Net gains (losses) arising during the period, Before Tax	37,204	(11,747)	(21,351)
Amortization of prior service cost, Before Tax	2,440	105	592
Amortization of net loss, Before Tax	(36,840)	17,608	1,540
Recognition of loss due to curtailment	750
Net change, Defined benefit pension plan, Before Tax	42,364	(9,241)	(19,219)
Total other comprehensive income (loss), Before Tax	21,965	18,122	(94,136)
Net gains (losses) arising during the period, Tax Effect	9,440	(4,311)	(925)
Less reclassification adjustment for net gains included in net income, Tax Effect	6,156	1,042	12,394
Net change in non-credit impairment losses on securities, Tax Effect	15,596	(3,269)	11,469
Net change in non-credit impairment losses on securities	(2,629)	(5,090)	15,875
Less reclassification adjustment for credit impairment losses included in net income, Tax Effect	193	(1,771)	(6,937)
Net change, Non-credit impairment losses on securities available for sale and held to maturity, Tax Effect	(2,436)	(6,861)	8,938
Net (losses) gains arising during the period, Tax Effect	(1,855)	2,422	10,236
Less reclassification adjustment for losses included in net income, Tax Effect	(2,893)	(2,718)	(1,287)
Net change, Unrealized gains and losses on derivatives (cash flow hedges), Tax Effect	(4,748)	(296)	8,949
Net gains (losses) arising during the period, Tax Effect	(15,627)	4,908	8,947
Amortization of prior service cost, Tax Effect	(119)	(944)	(244)
Amortization of net loss, Tax Effect	(825)	(1,005)	(645)
Recognition of loss due to curtailment	(282)
Net change, Defined benefit pension plan, Tax Effect	(17,720)	3,836	8,058
Total other comprehensive income (loss), Tax Effect	(9,308)	(6,590)	37,414
Net gains (losses) arising during the period, After Tax	(13,239)	5,682	1,513
Less reclassification adjustment for net gains included in net income, After Tax	(8,522)	(1,545)	(19,674)
Net change, Unrealized gains on AFS securities, After Tax	(21,761)	4,137	(18,161)
Net change in non-credit impairment losses on securities, After Tax	3,637	9,942	(26,656)
Less reclassification adjustment for credit impairment losses included in net income, After Tax	(268)	2,449	11,633
Defined benefit pension plan, total	3,369	12,391	(15,023)
Net gains (losses) arising during the period, After Tax	2,400	(3,351)	(14,157)
Less reclassification adjustment for losses included in net income, After Tax	4,005	3,760	1,780
Net change, Unrealized gains and losses on derivatives (cash flow hedges), After Tax	6,405	409	(12,377)
Net gains (losses) arising during the period, After Tax	21,577	(6,839)	(12,404)
Amortization of prior service cost, After Tax	1,454	38	348
Amortization of net loss, After Tax	1,145	1,396	895
Recognition of loss due to curtailment	468
Defined benefit pension plan, total	24,644	(5,405)	(11,161)
Total other comprehensive income (loss), After Tax	$ 12,657	$ 11,532	$ (56,722)