Loans and the Allowance for Credit Losses - Summary of Age Analysis of Loan Categories (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	$ 10,357,192	$ 10,789,233
90 Days or More Past Due and Accruing	8,318	8,846
Loans held for sale	41,461	168,378
Total loans, current	10,341,948	10,889,462
Total loans	10,398,653	10,957,611
Total Non-performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	42,011	40,807
Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	631,059	646,387
90 Days or More Past Due and Accruing	409	706
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	5,705,246	5,705,392
90 Days or More Past Due and Accruing	2,536	3,001
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	1,625,632	1,720,961
90 Days or More Past Due and Accruing	1,886	2,863
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	276,069	309,055
90 Days or More Past Due and Accruing	263	377
Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	588,218	668,277
90 Days or More Past Due and Accruing	83	288
Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	5,117,028	5,037,115
90 Days or More Past Due and Accruing	2,453	2,713
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	2,119,186	2,407,438
90 Days or More Past Due and Accruing	3,224	1,899
Non-Accrual Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	36,212	36,880
TDRs Accruing Interest [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	5,799	3,927
Current [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	10,300,487	10,721,084
Loans held for sale, current	41,461	168,378
Current [Member] | Total Non-performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	14,857	13,100
Current [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	625,173	639,319
Current [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	5,682,387	5,681,802
Current [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	1,610,608	1,698,636
Current [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	273,437	305,483
Current [Member] | Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	586,912	664,990
Current [Member] | Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	5,095,475	5,016,812
Current [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	2,108,882	2,395,844
Current [Member] | Non-Accrual Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	9,140	9,560
Current [Member] | TDRs Accruing Interest [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	5,717	3,540
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	13,567	16,856
30-59 Days Past Due [Member] | Total Non-performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	829	693
30-59 Days Past Due [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	2,135	2,414
30-59 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	6,666	5,458
30-59 Days Past Due [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	1,153	2,614
30-59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	1,649	1,998
30-59 Days Past Due [Member] | Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	1,149	582
30-59 Days Past Due [Member] | Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	5,517	4,876
30-59 Days Past Due [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	1,964	4,372
30-59 Days Past Due [Member] | Non-Accrual Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	825	630
30-59 Days Past Due [Member] | TDRs Accruing Interest [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	4	63
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	10,276	16,051
60-89 Days Past Due [Member] | Total Non-performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	1,781	618
60-89 Days Past Due [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	417	775
60-89 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	5,855	6,394
60-89 Days Past Due [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	2,260	5,654
60-89 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	648	1,031
60-89 Days Past Due [Member] | Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income		2,276
60-89 Days Past Due [Member] | Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	5,855	4,118
60-89 Days Past Due [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	1,096	2,197
60-89 Days Past Due [Member] | Non-Accrual Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	1,710	466
60-89 Days Past Due [Member] | TDRs Accruing Interest [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	71	152
90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	32,862	35,242
90 Days or More Past Due [Member] | Total Non-performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	24,544	26,396
90 Days or More Past Due [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	3,334	3,879
90 Days or More Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	10,338	11,738
90 Days or More Past Due [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	11,611	14,057
90 Days or More Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	335	543
90 Days or More Past Due [Member] | Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	157	429
90 Days or More Past Due [Member] | Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	10,181	11,309
90 Days or More Past Due [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	7,244	5,025
90 Days or More Past Due [Member] | Non-Accrual Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	24,537	26,224
90 Days or More Past Due [Member] | TDRs Accruing Interest [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	7	172
Total Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	56,705	68,149
Total Past Due [Member] | Total Non-performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	27,154	27,707
Total Past Due [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	5,886	7,068
Total Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	22,859	23,590
Total Past Due [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	15,024	22,325
Total Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	2,632	3,572
Total Past Due [Member] | Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	1,306	3,287
Total Past Due [Member] | Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	21,553	20,303
Total Past Due [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	10,304	11,594
Total Past Due [Member] | Non-Accrual Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	27,072	27,320
Total Past Due [Member] | TDRs Accruing Interest [Member]
Financing Receivable, Recorded Investment [Line Items]
Portfolio loans, net of unearned income	$ 82	$ 387