Loans and Leases and the Allowance for Credit Losses - Loan and Leases Considered Nonaccrual and Interest Income Recognized on Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Jan. 01, 2021	Mar. 31, 2020	Jan. 01, 2020
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	$ 1,001,103	$ 446,591	$ 1,001,103	$ 446,591
Amortized Cost without Allowance	1,240,954	710,059	1,240,954	710,059
Total	2,242,057	1,156,650	2,242,057	1,156,650
Amortized Cost					$ 1,957,106	$ 1,893,299	$ 1,061,748	$ 1,134,333
Interest Income Recognized	11,604	18,127	22,334	30,698
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	210,294	138,556	210,294	138,556
Amortized Cost without Allowance	119,746	146,098	119,746	146,098
Total	330,040	284,654	330,040	284,654
Amortized Cost					295,069	306,827	286,647	346,743
Interest Income Recognized	2,930	1,298	6,015	3,036
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	366,166	57,675	366,166	57,675
Amortized Cost without Allowance	715,380	114,813	715,380	114,813
Total	1,081,546	172,488	1,081,546	172,488
Amortized Cost					824,079	775,894	188,469	173,796
Interest Income Recognized	604	4,697	2,262	5,789
Residential Builder and Developer [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	1,093	1,748	1,093	1,748
Amortized Cost without Allowance	13,459		13,459
Total	14,552	1,748	14,552	1,748
Amortized Cost					1,224	1,094	3,204	4,708
Interest Income Recognized		11	33	59
Other Commercial Construction [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	20,717	42,969	20,717	42,969
Amortized Cost without Allowance	113,041	42,457	113,041	42,457
Total	133,758	85,426	133,758	85,426
Amortized Cost					126,225	114,039	34,935	35,881
Interest Income Recognized	274	5,716	315	6,577
Residential [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	191,965	80,772	191,965	80,772
Amortized Cost without Allowance	180,179	226,135	180,179	226,135
Total	372,144	306,907	372,144	306,907
Amortized Cost					385,508	365,729	293,638	322,504
Interest Income Recognized	6,296	5,029	10,794	11,848
Residential Limited Documentation [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	85,683	26,460	85,683	26,460
Amortized Cost without Allowance	51,000	92,235	51,000	92,235
Total	136,683	118,695	136,683	118,695
Amortized Cost					143,069	147,170	119,317	114,667
Interest Income Recognized	157	256	236	457
Home Equity Lines and Loans [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	38,860	38,890	38,860	38,890
Amortized Cost without Allowance	37,851	38,204	37,851	38,204
Total	76,711	77,094	76,711	77,094
Amortized Cost					79,188	79,392	63,071	65,039
Interest Income Recognized	993	760	1,945	2,219
Recreational Finance [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	16,620	16,264	16,620	16,264
Amortized Cost without Allowance	6,656	7,888	6,656	7,888
Total	23,276	24,152	23,276	24,152
Amortized Cost					27,218	25,519	13,405	14,308
Interest Income Recognized	159	154	314	306
Automobile [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	27,609	35,510	27,609	35,510
Amortized Cost without Allowance	3,481	7,226	3,481	7,226
Total	31,090	42,736	31,090	42,736
Amortized Cost					38,219	39,404	19,251	21,293
Interest Income Recognized	48	45	97	92
Other [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	42,096	7,747	42,096	7,747
Amortized Cost without Allowance	161	35,003	161	35,003
Total	42,257	42,750	42,257	42,750
Amortized Cost					$ 37,307	$ 38,231	$ 39,811	$ 35,394
Interest Income Recognized	$ 143	$ 161	$ 323	$ 315