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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	$ 1,472,359	$ 1,636,206	$ 1,469,226	$ 1,736,387
Allowance on acquired PCD loans	99,000		99,000
Provision for credit losses	302,000	(15,000)	312,000	(40,000)
Net charge-offs
Charge-offs	(75,614)	(80,369)	(126,652)	(203,294)
Recoveries	26,045	34,291	70,216	82,035
Net charge-offs	(49,569)	(46,078)	(56,436)	(121,259)
Ending balance	1,823,790	1,575,128	1,823,790	1,575,128
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	307,055	328,994	283,899	405,846
Allowance on acquired PCD loans	41,003		41,003
Provision for credit losses	95,917	15,100	124,642	(57,318)
Net charge-offs
Charge-offs	(37,925)	(40,095)	(57,159)	(67,040)
Recoveries	8,423	10,853	22,088	33,364
Net charge-offs	(29,502)	(29,242)	(35,071)	(33,676)
Ending balance	414,473	314,852	414,473	314,852
Commercial Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	539,444	716,098	557,239	670,719
Allowance on acquired PCD loans	55,812		55,812
Provision for credit losses	120,277	(24,805)	(89,339)	74,666
Net charge-offs
Charge-offs	(8,796)	(12,523)	(10,596)	(73,175)
Recoveries	1,656	1,193	16,599	7,753
Net charge-offs	(7,140)	(11,330)	6,003	(65,422)
Ending balance	708,393	679,963	708,393	679,963
Residential Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	72,581	89,789	71,726	103,590
Allowance on acquired PCD loans	1,833		1,833
Provision for credit losses	50,168	(12,069)	51,888	(25,504)
Net charge-offs
Charge-offs	(2,863)	(2,262)	(6,835)	(4,661)
Recoveries	2,607	2,411	5,714	4,444
Net charge-offs	(256)	149	(1,121)	(217)
Ending balance	124,326	77,869	124,326	77,869
Consumer [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	553,279	501,325	556,362	556,232
Allowance on acquired PCD loans	352		352
Provision for credit losses	35,638	6,774	46,131	(31,844)
Net charge-offs
Charge-offs	(26,030)	(25,489)	(52,062)	(58,418)
Recoveries	13,359	19,834	25,815	36,474
Net charge-offs	(12,671)	(5,655)	(26,247)	(21,944)
Ending balance	$ 576,598	$ 502,444	$ 576,598	$ 502,444