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		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jan. 01, 2021	Jun. 30, 2020	Jan. 01, 2020
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	$ 946,452	$ 558,807	$ 946,452	$ 558,807
Amortized Cost without Allowance	1,295,811	681,165	1,295,811	681,165
Total	2,242,263	1,239,972	2,242,263	1,239,972
Amortized Cost					$ 2,242,057	$ 1,893,299	$ 1,156,650	$ 1,134,333
Interest Income Recognized	15,571	12,255	37,905	42,953
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	171,040	264,515	171,040	264,515
Amortized Cost without Allowance	109,149	86,113	109,149	86,113
Total	280,189	350,628	280,189	350,628
Amortized Cost					330,040	306,827	284,654	346,743
Interest Income Recognized	4,646	5,999	10,661	9,035
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	332,014	86,199	332,014	86,199
Amortized Cost without Allowance	820,856	166,316	820,856	166,316
Total	1,152,870	252,515	1,152,870	252,515
Amortized Cost					1,081,546	775,894	172,488	173,796
Interest Income Recognized	2,256	993	4,518	6,782
Residential Builder and Developer [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	594	1,833	594	1,833
Total	594	1,833	594	1,833
Amortized Cost					14,552	1,094	1,748	4,708
Interest Income Recognized	206	114	239	173
Other Commercial Construction [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	36,750	15,441	36,750	15,441
Amortized Cost without Allowance	121,949	22,186	121,949	22,186
Total	158,699	37,627	158,699	37,627
Amortized Cost					133,758	114,039	85,426	35,881
Interest Income Recognized	255	232	570	6,809
Residential [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	196,918	66,302	196,918	66,302
Amortized Cost without Allowance	156,508	231,334	156,508	231,334
Total	353,426	297,636	353,426	297,636
Amortized Cost					372,144	365,729	306,907	322,504
Interest Income Recognized	6,809	3,410	17,603	15,258
Residential Limited Documentation [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	81,538	29,824	81,538	29,824
Amortized Cost without Allowance	44,991	85,959	44,991	85,959
Total	126,529	115,783	126,529	115,783
Amortized Cost					136,683	147,170	118,695	114,667
Interest Income Recognized	100	114	336	571
Home Equity Lines and Loans [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	38,582	36,134	38,582	36,134
Amortized Cost without Allowance	32,892	42,686	32,892	42,686
Total	71,474	78,820	71,474	78,820
Amortized Cost					76,711	79,392	77,094	65,039
Interest Income Recognized	979	1,017	2,924	3,236
Recreational Finance [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	18,428	17,637	18,428	17,637
Amortized Cost without Allowance	5,479	6,554	5,479	6,554
Total	23,907	24,191	23,907	24,191
Amortized Cost					23,276	25,519	24,152	14,308
Interest Income Recognized	164	155	478	461
Automobile [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	27,258	37,355	27,258	37,355
Amortized Cost without Allowance	3,744	5,019	3,744	5,019
Total	31,002	42,374	31,002	42,374
Amortized Cost					31,090	39,404	42,736	21,293
Interest Income Recognized	46	47	143	139
Other [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	43,330	3,567	43,330	3,567
Amortized Cost without Allowance	243	34,998	243	34,998
Total	43,573	38,565	43,573	38,565
Amortized Cost					$ 42,257	$ 38,231	$ 42,750	$ 35,394
Interest Income Recognized	$ 110	$ 174	$ 433	$ 489