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
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	$ (85,143)	$ (279,959)
Unrealized holding gains (losses), net, before tax	(32,025)	131,423
Foreign currency translation adjustment, before tax	684	(3,225)
Unrealized gains (losses) on cash flow hedges, before tax	(9,498)	456,333
Total other comprehensive income (loss) before reclassifications, before tax	(40,839)	584,531
Amortization of unrealized holding losses on held-to-maturity ("HTM") securities, before tax	990	772
Gains (Loss) realized in net income	(3)
Accretion of net gain (losses) on terminated cash flow hedges, before tax	(30)	(34)
Net yield adjustment from cash flow hedges currently in effect, before tax	(82,044)	(32,041)
Amortization of prior service credit, before tax	(1,050)	(1,050)
Amortization of actuarial losses, before tax	21,850	13,650
Total other comprehensive income (loss), before tax	(101,126)	565,828
Ending balance, before tax	(186,269)	285,869
Beginning balance, tax	22,111	73,279
Unrealized holding gains (losses), net, tax	8,907	(34,544)
Foreign currency translation adjustment, tax	(136)	282
Unrealized losses on cash flow hedges, tax	2,571	(119,970)
Total other comprehensive income (loss), tax	11,342	(154,232)
Amortization of unrealized holding losses on held-to-maturity ('HTM') securities, tax	(276)	(203)
Gains realized in net income, tax	1
Accretion of net gain on terminated cash flow hedges, tax	9	9
Net yield adjustment from cash flow hedges currently in effect, tax	22,215	8,423
Amortization of prior service credit, tax	384	276
Amortization of actuarial losses, tax	(7,995)	(3,588)
Total other comprehensive income (loss), tax	25,680	(149,315)
Ending balance, tax	47,791	(76,036)
Beginning balance, net of tax	(63,032)	(206,680)
Unrealized holding gains (losses), net of tax	(23,118)	96,879
Foreign currency translation adjustments	548	(2,943)
Unrealized gains (losses) on cash flow hedges, net of tax	(6,927)	336,363
Total other comprehensive income (loss) before reclassifications, net of tax	(29,497)	430,299
Amortization of unrealized holding losses on held-to-maturity ('HTM') securities, net of tax	714	569
Gains realized in net income, net of tax	(2)
Accretion of net gain on terminated cash flow hedges, net of tax	(21)	(25)
Net yield adjustment from cash flow hedges currently in effect, net of tax	(59,829)	(23,618)
Amortization of prior service credit, net of tax	(666)	(774)
Amortization of actuarial losses, net of tax	13,855	10,062
Total other comprehensive income (loss)	(75,446)	416,513
Ending balance, net of tax	(138,478)	209,833
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	(32,025)	131,423
Total other comprehensive income (loss) before reclassifications, before tax	(32,025)	131,423
Amortization of unrealized holding losses on held-to-maturity ("HTM") securities, before tax	990	772
Gains (Loss) realized in net income	(3)
Total other comprehensive income (loss), before tax	(31,038)	132,195
Ending balance, before tax	164,348	182,896
Total other comprehensive income (loss)	(22,406)
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	(1,050)	(1,050)
Amortization of actuarial losses, before tax	21,850	13,650
Total other comprehensive income (loss), before tax	20,800	12,600
Ending balance, before tax	(629,287)	(451,948)
Total other comprehensive income (loss)	13,189
Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	369,558	133,888
Foreign currency translation adjustment, before tax	684	(3,225)
Unrealized gains (losses) on cash flow hedges, before tax	(9,498)	456,333
Total other comprehensive income (loss) before reclassifications, before tax	(8,814)	453,108
Accretion of net gain (losses) on terminated cash flow hedges, before tax	(30)	(34)
Net yield adjustment from cash flow hedges currently in effect, before tax	(82,044)	(32,041)
Total other comprehensive income (loss), before tax	(90,888)	421,033
Ending balance, before tax	$ 278,670	$ 554,921