Loans and Leases and the Allowance for Credit Losses - Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 1,575,128	$ 1,638,236	$ 1,736,387	$ 1,051,071
Provision for credit losses	(20,000)	150,000	(60,000)	725,000
Net charge-offs
Charge-offs	(64,273)	(52,226)	(267,567)	(211,327)
Recoveries	24,169	22,495	106,204	61,304
Net charge-offs	(40,104)	(29,731)	(161,363)	(150,023)
Ending balance	1,515,024	1,758,505	1,515,024	1,758,505
Adoption of new accounting standard				132,457
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	314,852	398,257	405,846	366,094
Provision for credit losses	(292)	25,450	(57,610)	161,444
Net charge-offs
Charge-offs	(26,598)	(14,434)	(93,638)	(63,425)
Recoveries	3,785	4,475	37,149	11,109
Net charge-offs	(22,813)	(9,959)	(56,489)	(52,316)
Ending balance	291,747	413,748	291,747	413,748
Adoption of new accounting standard				(61,474)
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	679,963	576,321	670,719	322,201
Provision for credit losses	(42,016)	87,403	32,650	335,159
Net charge-offs
Charge-offs	(14,242)	(4,522)	(87,417)	(23,266)
Recoveries	2,362	2,578	10,115	4,030
Net charge-offs	(11,880)	(1,944)	(77,302)	(19,236)
Ending balance	626,067	661,780	626,067	661,780
Adoption of new accounting standard				23,656
One-to-Four Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	77,869	118,921	103,590	56,033
Provision for credit losses	(3,522)	(683)	(29,026)	11,458
Net charge-offs
Charge-offs	(1,925)	(1,516)	(6,586)	(8,227)
Recoveries	1,903	960	6,347	4,522
Net charge-offs	(22)	(556)	(239)	(3,705)
Ending balance	74,325	117,682	74,325	117,682
Adoption of new accounting standard				53,896
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	502,444	544,737	556,232	229,118
Provision for credit losses	25,830	37,830	(6,014)	216,939
Net charge-offs
Charge-offs	(21,508)	(31,754)	(79,926)	(116,409)
Recoveries	16,119	14,482	52,593	41,643
Net charge-offs	(5,389)	(17,272)	(27,333)	(74,766)
Ending balance	$ 522,885	$ 565,295	$ 522,885	565,295
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)