Loans and Leases and the Allowance for Credit Losses - Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 1,469,226	$ 1,736,387
Provision for credit losses	10,000	(25,000)
Net charge-offs
Charge-offs	(51,038)	(122,925)
Recoveries	44,171	47,744
Net (charge-offs) recoveries	6,867	(75,181)
Ending balance	1,472,359	1,636,206
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	283,899	405,846
Provision for credit losses	28,725	(72,418)
Net charge-offs
Charge-offs	(19,234)	(26,945)
Recoveries	13,665	22,511
Net (charge-offs) recoveries	5,569	(4,434)
Ending balance	307,055	328,994
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	557,239	670,719
Provision for credit losses	(30,938)	99,471
Net charge-offs
Charge-offs	(1,800)	(60,652)
Recoveries	14,943	6,560
Net (charge-offs) recoveries	(13,143)	(54,092)
Ending balance	539,444	716,098
One-to-Four Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	71,726	103,590
Provision for credit losses	1,720	(13,435)
Net charge-offs
Charge-offs	(3,972)	(2,399)
Recoveries	3,107	2,033
Net (charge-offs) recoveries	865	(366)
Ending balance	72,581	89,789
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	556,362	556,232
Provision for credit losses	10,493	(38,618)
Net charge-offs
Charge-offs	(26,032)	(32,929)
Recoveries	12,456	16,640
Net (charge-offs) recoveries	13,576	(16,289)
Ending balance	$ 553,279	$ 501,325