Allowance for Credit Losses - Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 1,736,387	$ 1,051,071	$ 1,019,444
Provision for credit losses	(75,000)	800,000	176,000
Net charge-offs
Charge-offs	(338,154)	(333,507)	(237,708)
Recoveries	145,993	86,366	93,335
Net charge-offs	(192,161)	(247,141)	(144,373)
Ending balance	1,469,226	1,736,387	1,051,071
Adoption of new accounting standard		132,457
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	405,846	366,094	330,055
Provision for credit losses	(40,378)	220,544	69,702
Net charge-offs
Charge-offs	(122,651)	(135,083)	(58,244)
Recoveries	41,082	15,765	24,581
Net charge-offs	(81,569)	(119,318)	(33,663)
Ending balance	283,899	405,846	366,094
Adoption of new accounting standard		(61,474)
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	670,719	322,201	341,655
Provision for credit losses	(42,825)	356,203	(10,726)
Net charge-offs
Charge-offs	(101,306)	(35,891)	(12,664)
Recoveries	30,651	4,550	3,936
Net charge-offs	(70,655)	(31,341)	(8,728)
Ending balance	557,239	670,719	322,201
Adoption of new accounting standard		23,656
One-to-Four Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	103,590	56,033	69,125
Provision for credit losses	(29,817)	(3,172)	(8,585)
Net charge-offs
Charge-offs	(10,904)	(10,283)	(12,711)
Recoveries	8,857	7,116	8,204
Net charge-offs	(2,047)	(3,167)	(4,507)
Ending balance	71,726	103,590	56,033
Adoption of new accounting standard		53,896
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	556,232	229,118	200,564
Provision for credit losses	38,020	226,425	126,029
Net charge-offs
Charge-offs	(103,293)	(152,250)	(154,089)
Recoveries	65,403	58,935	56,614
Net charge-offs	(37,890)	(93,315)	(97,475)
Ending balance	$ 556,362	556,232	229,118
Adoption of new accounting standard		194,004
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance		77,625	78,045
Provision for credit losses			(420)
Net charge-offs
Ending balance			$ 77,625
Adoption of new accounting standard		$ (77,625)