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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Jan. 01, 2020	Jun. 30, 2019	Jan. 01, 2019
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	$ 558,807	$ 413,503	$ 558,807	$ 413,503
Amortized Cost without Allowance	681,165	591,746	681,165	591,746
Total	1,239,972	1,005,249	1,239,972	1,005,249
Amortized Cost					$ 1,156,650	$ 1,134,333	$ 865,384	$ 893,608
Interest Income Recognized	12,255	9,101	42,953	31,151
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	264,515	223,183	264,515	223,183
Amortized Cost without Allowance	86,113	159,626	86,113	159,626
Total	350,628	382,809	350,628	382,809
Amortized Cost					284,654	346,743	223,733	234,423
Interest Income Recognized	5,999	836	9,035	7,552
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	86,199	40,203	86,199	40,203
Amortized Cost without Allowance	166,316	144,429	166,316	144,429
Total	252,515	184,632	252,515	184,632
Amortized Cost					172,488	173,796	203,116	203,672
Interest Income Recognized	993	1,802	6,782	5,212
Residential Builder and Developer [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	1,833	1,596	1,833	1,596
Amortized Cost without Allowance		3,379		3,379
Total	1,833	4,975	1,833	4,975
Amortized Cost					1,748	4,708	5,985	4,798
Interest Income Recognized	114	89	173	308
Other Commercial Construction [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	15,441	15,501	15,441	15,501
Amortized Cost without Allowance	22,186	15,940	22,186	15,940
Total	37,627	31,441	37,627	31,441
Amortized Cost					85,426	35,881	32,769	22,205
Interest Income Recognized	232	488	6,809	1,669
Residential [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	66,302	57,070	66,302	57,070
Amortized Cost without Allowance	231,334	166,496	231,334	166,496
Total	297,636	223,566	297,636	223,566
Amortized Cost					306,907	322,504	210,922	233,352
Interest Income Recognized	3,410	3,425	15,258	10,014
Residential Limited Documentation [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	29,824	27,803	29,824	27,803
Amortized Cost without Allowance	85,959	53,876	85,959	53,876
Total	115,783	81,679	115,783	81,679
Amortized Cost					118,695	114,667	87,551	84,685
Interest Income Recognized	114	269	571	795
Home Equity Lines and Loans [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	36,134	23,908	36,134	23,908
Amortized Cost without Allowance	42,686	36,007	42,686	36,007
Total	78,820	59,915	78,820	59,915
Amortized Cost					77,094	65,039	66,927	71,292
Interest Income Recognized	1,017	1,846	3,236	4,617
Recreational Finance [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	17,637	6,577	17,637	6,577
Amortized Cost without Allowance	6,554	5,275	6,554	5,275
Total	24,191	11,852	24,191	11,852
Amortized Cost					24,152	14,308	11,153	11,199
Interest Income Recognized	155	147	461	431
Automobile [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	37,355	14,596	37,355	14,596
Amortized Cost without Allowance	5,019	6,443	5,019	6,443
Total	42,374	21,039	42,374	21,039
Amortized Cost					42,736	21,293	20,170	23,359
Interest Income Recognized	47	54	139	161
Other [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	3,567	3,066	3,567	3,066
Amortized Cost without Allowance	34,998	275	34,998	275
Total	38,565	3,341	38,565	3,341
Amortized Cost					$ 42,750	$ 35,394	$ 3,058	$ 4,623
Interest Income Recognized	$ 174	$ 145	$ 489	$ 392