Loans and Leases and the Allowance for Credit Losses - Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 1,636,206	$ 1,384,366	$ 1,736,387	$ 1,051,071
Provision for credit losses	(15,000)	325,000	(40,000)	575,000
Net charge-offs
Charge-offs	(80,369)	(91,397)	(203,294)	(159,101)
Recoveries	34,291	20,267	82,035	38,809
Net (charge-offs) recoveries	(46,078)	(71,130)	(121,259)	(120,292)
Ending balance	1,575,128	1,638,236	1,575,128	1,638,236
Adoption of new accounting standard				132,457
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	328,994	358,092	405,846	366,094
Provision for credit losses	15,100	69,400	(57,318)	135,994
Net charge-offs
Charge-offs	(40,095)	(32,608)	(67,040)	(48,991)
Recoveries	10,853	3,373	33,364	6,634
Net (charge-offs) recoveries	(29,242)	(29,235)	(33,676)	(42,357)
Ending balance	314,852	398,257	314,852	398,257
Adoption of new accounting standard				(61,474)
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	716,098	433,689	670,719	322,201
Provision for credit losses	(24,805)	159,090	74,666	247,756
Net charge-offs
Charge-offs	(12,523)	(17,472)	(73,175)	(18,744)
Recoveries	1,193	1,014	7,753	1,452
Net (charge-offs) recoveries	(11,330)	(16,458)	(65,422)	(17,292)
Ending balance	679,963	576,321	679,963	576,321
Adoption of new accounting standard				23,656
One-to-Four Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	89,789	115,792	103,590	56,033
Provision for credit losses	(12,069)	2,850	(25,504)	12,141
Net charge-offs
Charge-offs	(2,262)	(1,609)	(4,661)	(6,711)
Recoveries	2,411	1,888	4,444	3,562
Net (charge-offs) recoveries	149	279	(217)	(3,149)
Ending balance	77,869	118,921	77,869	118,921
Adoption of new accounting standard				53,896
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	501,325	476,793	556,232	229,118
Provision for credit losses	6,774	93,660	(31,844)	179,109
Net charge-offs
Charge-offs	(25,489)	(39,708)	(58,418)	(84,655)
Recoveries	19,834	13,992	36,474	27,161
Net (charge-offs) recoveries	(5,655)	(25,716)	(21,944)	(57,494)
Ending balance	$ 502,444	$ 544,737	$ 502,444	544,737
Adoption of new accounting standard				194,004
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				77,625
Net charge-offs
Adoption of new accounting standard				$ (77,625)