Loans and Leases (Allowance For Loan And Lease Losses By Portfolio Segment) (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	$ 328,351	$ 334,931	$ 359,431	$ 209,096
(Benefit) provision	(21,574)	40,003	(47,333)	116,088
Charge-offs	(3,402)	(18,074)	(12,697)	(28,235)
Recoveries	4,570	1,662	8,544	4,005
Balance, end of period	307,945	358,522	307,945	358,522	$ 359,431
ALLL, Individually evaluated for impairment	16,097	19,755	16,097	19,755
ALLL, Collectively evaluated for impairment	291,848	338,767	291,848	338,767
Loan and lease balances, Individually evaluated for impairment	239,458	323,156	239,458	323,156
Loan and lease balances, Collectively evaluated for impairment	21,235,543	21,479,361	21,235,543	21,479,361
Loans and leases	21,475,001	21,802,517	21,475,001	21,802,517	21,641,215
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period			0	57,568
Balance, end of period					0
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	283,906	261,926	312,244	161,669
(Benefit) provision	(21,077)	44,605	(44,730)	115,848
Charge-offs	(594)	(15,294)	(6,915)	(20,868)
Recoveries	836	283	2,472	847
Balance, end of period	263,071	291,520	263,071	291,520	312,244
ALLL, Individually evaluated for impairment	11,537	15,271	11,537	15,271
ALLL, Collectively evaluated for impairment	251,534	276,249	251,534	276,249
Loan and lease balances, Individually evaluated for impairment	128,937	165,010	128,937	165,010
Loan and lease balances, Collectively evaluated for impairment	14,699,454	14,589,073	14,699,454	14,589,073
Loans and leases	14,828,391	14,754,083	14,828,391	14,754,083	14,900,535
Commercial Portfolio Segment [Member] \| Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period			0	34,024
Balance, end of period					0
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	44,445	73,005	47,187	47,427
(Benefit) provision	(497)	(4,602)	(2,603)	240
Charge-offs	(2,808)	(2,780)	(5,782)	(7,367)
Recoveries	3,734	1,379	6,072	3,158
Balance, end of period	44,874	67,002	44,874	67,002	47,187
ALLL, Individually evaluated for impairment	4,560	4,484	4,560	4,484
ALLL, Collectively evaluated for impairment	40,314	62,518	40,314	62,518
Loan and lease balances, Individually evaluated for impairment	110,521	158,146	110,521	158,146
Loan and lease balances, Collectively evaluated for impairment	6,536,089	6,890,288	6,536,089	6,890,288
Loans and leases	$ 6,646,610	$ 7,048,434	6,646,610	7,048,434	6,740,680
Consumer Portfolio Segment [Member] \| Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period			$ 0	$ 23,544
Balance, end of period					$ 0

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount excluding accrued interest, before allowance for credit loss, of financing receivable.

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The balance of financing receivables that were individually evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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