Reclassifications of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gain on securities		$ 7,725	$ (14)	$ 29,924
Interest expense		847,760	658,678	452,236
Income tax expenses\ benefit		(128,264)	(135,252)	(202,014)
Net income		395,043	$ 422,417	$ 466,201
Reclassifications, net of tax	[1]	(3,156)
Past service liability
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, before tax	[1],[2]	249
Actuarial losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, before tax	[1],[2]	(10,160)
Amortization of defined benefit pension
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, before tax	[1]	(9,911)
Tax benefit	[1]	2,726
Reclassifications, net of tax	[1]	(7,185)
Reclassification out of Accumulated Other Comprehensive Income (loss) | Unrealized gains on available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gain on securities	[1]	5,445
Income tax expenses\ benefit	[1]	(1,527)
Net income	[1]	3,918
Reclassification out of Accumulated Other Comprehensive Income (loss) | Unrealized gains (loss) on cash flow hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	[1]	154
Income tax expenses\ benefit	[1]	(43)
Net income	[1]	$ 111

[1] Amounts in parentheses indicate expense items.

[2] See Note 14, “Employee Benefits,” for additional information.