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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax			$ (85,143)	$ (279,959)
Unrealized holding gains (losses), net, before tax			(43,732)	177,086
Foreign currency translation adjustment, before tax			881	(3,624)
Unrealized gains (losses) on cash flow hedges, before tax			(5,969)	511,195
Total other comprehensive income (loss) before reclassifications			(48,820)	684,657
Amortization of unrealized holding losses on held-to-maturity ("HTM") securities, before tax			2,232	1,619
Gains (Loss) realized in net income			(4)
Accretion of net gain (losses) on terminated cash flow hedges, before tax			(60)	(64)
Net yield adjustment from cash flow hedges currently in effect, before tax			(148,655)	(101,194)
Amortization of prior service credit, before tax			(2,093)	(2,090)
Amortization of actuarial losses, before tax			43,862	28,430
Total other comprehensive income (loss), before tax			(153,538)	611,358
Ending balance, before tax	$ (238,681)	$ 331,399	(238,681)	331,399
Beginning balance, tax			22,111	73,279
Unrealized holding gains (losses), net, tax			11,596	(45,856)
Foreign currency translation adjustment, tax			(188)	630
Unrealized losses on cash flow hedges, tax			1,565	(132,404)
Total other comprehensive income (loss) before reclassifications			12,973	(177,630)
Amortization of unrealized holding losses on held-to-maturity ('HTM') securities, tax			(587)	(450)
Gains realized in net income, tax			1
Accretion of net gain on terminated cash flow hedges, tax			17	18
Net yield adjustment from cash flow hedges currently in effect, tax			38,965	26,210
Amortization of prior service credit, tax			590	650
Amortization of actuarial losses, tax			(12,363)	(8,846)
Total other comprehensive income (loss), tax			39,596	(160,048)
Ending balance, tax	61,707	(86,769)	61,707	(86,769)
Beginning balance, net of tax			(63,032)	(206,680)
Unrealized holding gains (losses), net of tax			(32,136)	131,230
Foreign currency translation adjustments	145	(51)	693	(2,994)
Unrealized gains (losses) on cash flow hedges, net of tax			(4,404)	378,791
Total other comprehensive income (loss) before reclassifications			(35,847)	507,027
Amortization of unrealized holding losses on held-to-maturity ('HTM') securities, net of tax			1,645	1,169
Gains realized in net income, net of tax			(3)
Accretion of net gain on terminated cash flow hedges, net of tax			(43)	(46)
Net yield adjustment from cash flow hedges currently in effect, net of tax			(109,690)	(74,984)
Amortization of prior service credit, net of tax			(1,503)	(1,440)
Amortization of actuarial losses, net of tax			31,499	19,584
Total other comprehensive income (loss)	(38,496)	34,797	(113,942)	451,310
Ending balance, net of tax	(176,974)	244,630	(176,974)	244,630
Investment Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax			195,386	50,701
Unrealized holding gains (losses), net, before tax			(43,732)	177,086
Total other comprehensive income (loss) before reclassifications			(43,732)	177,086
Amortization of unrealized holding losses on held-to-maturity ("HTM") securities, before tax			2,232	1,619
Gains (Loss) realized in net income			(4)
Total other comprehensive income (loss), before tax			(41,504)	178,705
Ending balance, before tax	153,882	229,406	153,882	229,406
Total other comprehensive income (loss)			(30,494)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax			(650,087)	(464,548)
Amortization of prior service credit, before tax			(2,093)	(2,090)
Amortization of actuarial losses, before tax			43,862	28,430
Total other comprehensive income (loss), before tax			41,769	26,340
Ending balance, before tax	(608,318)	(438,208)	(608,318)	(438,208)
Total other comprehensive income (loss)			29,996
Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax			369,558	133,888
Foreign currency translation adjustment, before tax			881	(3,624)
Unrealized gains (losses) on cash flow hedges, before tax			(5,969)	511,195
Total other comprehensive income (loss) before reclassifications			(5,088)	507,571
Accretion of net gain (losses) on terminated cash flow hedges, before tax			(60)	(64)
Net yield adjustment from cash flow hedges currently in effect, before tax			(148,655)	(101,194)
Total other comprehensive income (loss), before tax			(153,803)	406,313
Ending balance, before tax	$ 215,755	$ 540,201	$ 215,755	$ 540,201