Comprehensive Income - Components of Other Comprehensive Income (Loss) and Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) to Net Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Components Of Comprehensive Income [Line Items]
Beginning balance	$ (105,797)	$ (395,657)
Unrealized holding gains (losses), net	62,087	5,581
Foreign currency translation adjustment	(234)	(1,452)
Total other comprehensive income before reclassifications	61,853	4,129
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	825	1,195
OTTI charges recognized in net income		9,800
Amortization of prior service credit	(2,000)	(2,000)
Amortization of actuarial losses	3,350	10,500
Total reclassifications	2,175	19,495
Total gain (loss) during the period	64,028	23,624
Ending balance	(41,769)	(372,033)
Beginning balance	41,638	155,393
Unrealized holding gains (losses), net	(24,374)	(2,181)
Foreign currency translation adjustment	98	520
Total other comprehensive income before reclassifications	(24,276)	(1,661)
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	(324)	(469)
OTTI charges recognized in net income		(3,847)
Amortization of prior service credit	785	785
Amortization of actuarial losses	(1,315)	(4,121)
Total reclassifications	(854)	(7,652)
Total gain (loss) during the period	(25,130)	(9,313)
Ending balance	16,508	146,080
Beginning balance	(64,159)	(240,264)
Unrealized holding gains (losses), net	37,713	3,400
Foreign currency translation adjustment	(136)	(932)
Total other comprehensive income before reclassifications	37,577	2,468
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	501	726
OTTI charges recognized in net income		5,953
Amortization of prior service credit	(1,215)	(1,215)
Amortization of actuarial losses	2,035	6,379
Total reclassifications	1,321	11,843
Total gain (loss) during the period	38,898	14,311
Ending Balance	(25,261)	(225,953)
Investment Securities With OTTI [Member]
Components Of Comprehensive Income [Line Items]
Beginning balance	37,255	(91,835)
Unrealized holding gains (losses), net	19,968	24,540
Foreign currency translation adjustment
Total other comprehensive income before reclassifications	19,968	24,540
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	2	49
OTTI charges recognized in net income		9,800
Amortization of prior service credit
Amortization of actuarial losses
Total reclassifications	2	9,849
Total gain (loss) during the period	19,970	34,389
Ending balance	57,225	(57,446)
Investment Securities All Other [Member]
Components Of Comprehensive Income [Line Items]
Beginning balance	18,450	152,199
Unrealized holding gains (losses), net	42,119	(18,959)
Foreign currency translation adjustment
Total other comprehensive income before reclassifications	42,119	(18,959)
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	823	1,146
OTTI charges recognized in net income
Amortization of prior service credit
Amortization of actuarial losses
Total reclassifications	823	1,146
Total gain (loss) during the period	42,942	(17,813)
Ending balance	61,392	134,386
Defined Benefit Plans [Member]
Components Of Comprehensive Income [Line Items]
Beginning balance	(161,617)	(455,590)
Unrealized holding gains (losses), net
Foreign currency translation adjustment
Total other comprehensive income before reclassifications
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities
OTTI charges recognized in net income
Amortization of prior service credit	(2,000)	(2,000)
Amortization of actuarial losses	3,350	10,500
Total reclassifications	1,350	8,500
Total gain (loss) during the period	1,350	8,500
Ending balance	(160,267)	(447,090)
Beginning balance	(98,182)
Total gain (loss) during the period	820
Ending Balance	(97,362)
Other [Member]
Components Of Comprehensive Income [Line Items]
Beginning balance	115	(431)
Unrealized holding gains (losses), net
Foreign currency translation adjustment	(234)	(1,452)
Total other comprehensive income before reclassifications	(234)	(1,452)
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities
OTTI charges recognized in net income
Amortization of prior service credit
Amortization of actuarial losses
Total reclassifications
Total gain (loss) during the period	(234)	(1,452)
Ending balance	$ (119)	$ (1,883)