Comprehensive Income - Components of Other Comprehensive Income (Loss) and Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) to Net Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax			$ (279,959)	$ (569,328)
Unrealized holding gains (losses), net, before tax			151,777	237,615
Foreign currency translation adjustment, before tax			(222)	(2,663)
Unrealized gains (losses) on cash flow hedges, before tax			508,226	204,587
Total other comprehensive income (loss) before reclassifications, before tax			659,781	439,539
Amortization of unrealized holding losses on held-to-maturity ("HTM") securities, before tax			2,678	2,524
Gains (Loss) realized in net income			(3)	7
Accretion of net gain on terminated cash flow hedges, before tax			(94)	(93)
Net yield adjustment from cash flow hedges currently in effect, before tax			(183,598)	6,693
Amortization of prior service credit, before tax			(3,140)	(3,129)
Amortization of actuarial losses, before tax			42,080	15,559
Total other comprehensive income (loss), before tax			517,704	461,100
Ending balance, before tax	$ 237,745	$ (108,228)	237,745	(108,228)
Beginning balance, before tax			73,279	149,247
Unrealized holding gains (losses), net, before tax			(39,277)	(62,432)
Foreign currency translation adjustment, before tax			(39)	559
Unrealized gains (losses) on cash flow hedges, before tax			(131,504)	(53,786)
Total other comprehensive income (loss) before reclassifications, before tax			(170,820)	(115,659)
Amortization of unrealized holding losses on held-to-maturity ("HTM") securities, before tax			(725)	(663)
Gains (Loss) realized in net income			1	(2)
Accretion of net gain on terminated cash flow hedges, before tax			26	25
Net yield adjustment from cash flow hedges currently in effect, before tax			47,506	(1,760)
Amortization of prior service credit, before tax			927	823
Amortization of actuarial losses, before tax			(12,436)	(4,091)
Total other comprehensive income (loss), before tax			(135,521)	(121,327)
Ending balance, before tax	(62,242)	27,920	(62,242)	27,920
Unrealized holding gains (losses), net, before tax			(39,277)	(62,432)
Beginning balance, before tax			(206,680)	(420,081)
Unrealized holding gains (losses), net, before tax			112,500	175,183
Foreign currency translation adjustments	2,733	(1,704)	(261)	(2,104)
Unrealized gains (losses) on cash flow hedges, before tax			376,722	150,801
Total other comprehensive income (loss) before reclassifications, before tax			488,961	323,880
Amortization of unrealized holding losses on held-to-maturity ("HTM") securities, before tax			1,953	1,861
Gains (Loss) realized in net income			(2)	(5)
Accretion of net gain on terminated cash flow hedges, before tax			(68)	(68)
Net yield adjustment from cash flow hedges currently in effect, before tax			(136,092)	4,933
Amortization of prior service credit, before tax			(2,213)	(2,306)
Amortization of actuarial losses, before tax			29,644	(11,468)
Total other comprehensive income (loss)	(69,127)	32,650	382,183	339,773
Ending balance, before tax	175,503	(80,308)	175,503	(80,308)
Losses realized in net income, net of tax			2	5
Amortization of actuarial losses, net of tax			(29,644)	11,468
Investment Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax			50,701	(200,107)
Unrealized holding gains (losses), net, before tax			151,777	237,615
Total other comprehensive income (loss) before reclassifications, before tax			151,777	237,615
Amortization of unrealized holding losses on held-to-maturity ("HTM") securities, before tax			2,678	2,524
Gains (Loss) realized in net income			(3)	7
Total other comprehensive income (loss), before tax			154,452	240,146
Ending balance, before tax	205,153	40,039	205,153	40,039
Total other comprehensive income (loss)			114,451
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax			(464,548)	(354,502)
Amortization of prior service credit, before tax			(3,140)	(3,129)
Amortization of actuarial losses, before tax			42,080	15,559
Total other comprehensive income (loss), before tax			38,940	12,430
Ending balance, before tax	(425,608)	(342,072)	(425,608)	(342,072)
Total other comprehensive income (loss)			27,431
Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax			133,888	(14,719)
Foreign currency translation adjustment, before tax			(222)	(2,663)
Unrealized gains (losses) on cash flow hedges, before tax			508,226	204,587
Total other comprehensive income (loss) before reclassifications, before tax			508,004	201,924
Accretion of net gain on terminated cash flow hedges, before tax			(94)	(93)
Net yield adjustment from cash flow hedges currently in effect, before tax			(183,598)	6,693
Total other comprehensive income (loss), before tax			324,312	208,524
Ending balance, before tax	$ 458,200	$ 193,805	$ 458,200	$ 193,805