Allowance for Loan Losses, Allowance for Losses on Lending-Related Commitments and Impaired Loans (Schedule of Aging of the Company's Loan Portfolio) (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Financing Receivable, Past Due [Line Items]
Nonaccrual	$ 105,847	$ 105,326	$ 77,899
90+ days and still accruing	16,105	18,872	10,993
Current	24,998,685	23,526,168	22,398,659
Loans, net of unearned income, excluding covered loans	25,304,659	23,820,691	22,610,560
60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	54,908	34,176	46,588
30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	129,114	136,149	76,421
Commercial
Financing Receivable, Past Due [Line Items]
Nonaccrual	47,604	50,984	18,388
90+ days and still accruing	1,939	3,313	882
Current	8,199,846	7,737,729	7,250,803
Loans, net of unearned income, excluding covered loans	8,270,774	7,828,538	7,289,060
Commercial | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	5,283	1,651	3,064
Commercial | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	16,102	34,861	15,923
Commercial | Commercial, industrial and other
Financing Receivable, Past Due [Line Items]
Nonaccrual	35,902	34,298	13,543
90+ days and still accruing	488	0	0
Current	5,245,403	5,062,729	4,597,666
Loans, net of unearned income, excluding covered loans	5,295,775	5,120,096	4,621,789
Commercial | Commercial, industrial and other | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	3,711	1,451	1,384
Commercial | Commercial, industrial and other | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	10,271	21,618	9,196
Commercial | Franchise
Financing Receivable, Past Due [Line Items]
Nonaccrual	11,076	16,051	2,438
90+ days and still accruing	0	0	0
Current	915,445	924,190	954,493
Loans, net of unearned income, excluding covered loans	926,521	948,979	957,339
Commercial | Franchise | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	0	0	408
Commercial | Franchise | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	0	8,738	0
Commercial | Mortgage warehouse lines of credit
Financing Receivable, Past Due [Line Items]
Nonaccrual	0	0	0
90+ days and still accruing	0	0	0
Current	275,170	144,199	200,060
Loans, net of unearned income, excluding covered loans	275,170	144,199	200,060
Commercial | Mortgage warehouse lines of credit | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	0	0	0
Commercial | Mortgage warehouse lines of credit | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	0	0	0
Commercial | Asset-based lending
Financing Receivable, Past Due [Line Items]
Nonaccrual	568	635	2,158
90+ days and still accruing	0	0	0
Current	1,062,411	1,022,065	1,033,040
Loans, net of unearned income, excluding covered loans	1,068,226	1,026,056	1,042,755
Commercial | Asset-based lending | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	972	200	1,146
Commercial | Asset-based lending | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	4,275	3,156	6,411
Commercial | Leases
Financing Receivable, Past Due [Line Items]
Nonaccrual	58	0	249
90+ days and still accruing	0	0	0
Current	679,891	564,430	458,276
Loans, net of unearned income, excluding covered loans	680,757	565,680	458,614
Commercial | Leases | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	0	0	0
Commercial | Leases | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	808	1,250	89
Commercial | PCI - commercial
Financing Receivable, Past Due [Line Items]
Nonaccrual	0	0	0
90+ days and still accruing	1,451	3,313	882
Current	21,526	20,116	7,268
Loans, net of unearned income, excluding covered loans	24,325	23,528	8,503
Commercial | PCI - commercial | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	600	0	126
Commercial | PCI - commercial | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	748	99	227
Commercial real estate
Financing Receivable, Past Due [Line Items]
Nonaccrual	20,875	19,129	19,195
90+ days and still accruing	5,124	6,241	3,194
Current	7,166,059	6,845,490	6,520,894
Loans, net of unearned income, excluding covered loans	7,276,244	6,933,252	6,575,084
Commercial real estate | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	11,199	10,826	4,119
Commercial real estate | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	72,987	51,566	27,682
Commercial real estate | Construction
Financing Receivable, Past Due [Line Items]
Nonaccrual	1,030	1,554	1,554
90+ days and still accruing	0	0	0
Current	813,767	749,846	804,583
Loans, net of unearned income, excluding covered loans	838,499	760,824	807,235
Commercial real estate | Construction | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	0	0	0
Commercial real estate | Construction | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	23,702	9,424	1,098
Commercial real estate | Land
Financing Receivable, Past Due [Line Items]
Nonaccrual	1,226	107	228
90+ days and still accruing	0	0	0
Current	142,186	141,097	114,651
Loans, net of unearned income, excluding covered loans	145,639	141,481	115,357
Commercial real estate | Land | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	0	170	0
Commercial real estate | Land | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	2,227	107	478
Commercial real estate | Office
Financing Receivable, Past Due [Line Items]
Nonaccrual	8,981	3,629	1,333
90+ days and still accruing	0	0	0
Current	932,749	929,739	891,406
Loans, net of unearned income, excluding covered loans	957,218	939,322	894,349
Commercial real estate | Office | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	892	877	207
Commercial real estate | Office | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	14,596	5,077	1,403
Commercial real estate | Industrial
Financing Receivable, Past Due [Line Items]
Nonaccrual	368	285	185
90+ days and still accruing	0	0	0
Current	954,736	885,367	881,214
Loans, net of unearned income, excluding covered loans	956,530	902,248	882,525
Commercial real estate | Industrial | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	552	0	0
Commercial real estate | Industrial | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	874	16,596	1,126
Commercial real estate | Retail
Financing Receivable, Past Due [Line Items]
Nonaccrual	6,867	10,753	11,540
90+ days and still accruing	0	0	0
Current	959,080	878,106	850,254
Loans, net of unearned income, excluding covered loans	976,201	892,478	867,639
Commercial real estate | Retail | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	1,232	1,890	372
Commercial real estate | Retail | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	9,022	1,729	5,473
Commercial real estate | Multi-family
Financing Receivable, Past Due [Line Items]
Nonaccrual	296	311	342
90+ days and still accruing	0	0	0
Current	1,235,814	970,597	951,095
Loans, net of unearned income, excluding covered loans	1,240,067	976,560	952,048
Commercial real estate | Multi-family | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	0	77	0
Commercial real estate | Multi-family | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	3,957	5,575	611
Commercial real estate | Mixed use and other
Financing Receivable, Past Due [Line Items]
Nonaccrual	2,107	2,490	4,013
90+ days and still accruing	0	0	0
Current	2,014,917	2,192,105	1,934,965
Loans, net of unearned income, excluding covered loans	2,035,099	2,205,195	1,949,242
Commercial real estate | Mixed use and other | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	5,520	1,617	408
Commercial real estate | Mixed use and other | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	12,555	8,983	9,856
Commercial real estate | PCI - commercial real estate
Financing Receivable, Past Due [Line Items]
Nonaccrual	0	0	0
90+ days and still accruing	5,124	6,241	3,194
Current	112,810	98,633	92,726
Loans, net of unearned income, excluding covered loans	126,991	115,144	106,689
Commercial real estate | PCI - commercial real estate | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	3,003	6,195	3,132
Commercial real estate | PCI - commercial real estate | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	6,054	4,075	7,637
Home equity
Financing Receivable, Past Due [Line Items]
Nonaccrual	8,489	7,147	9,096
90+ days and still accruing	0	0	0
Current	516,405	541,960	581,178
Loans, net of unearned income, excluding covered loans	527,370	552,343	593,500
Home equity | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	321	131	0
Home equity | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	2,155	3,105	3,226
Residential real estate
Financing Receivable, Past Due [Line Items]
Nonaccrual	14,236	16,383	15,825
90+ days and still accruing	1,867	1,292	1,472
Current	1,098,937	976,926	873,002
Loans, net of unearned income, excluding covered loans	1,118,178	1,002,464	895,470
Residential real estate | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	1,306	1,692	3,637
Residential real estate | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	1,832	6,171	1,534
Premium finance receivables | Commercial
Financing Receivable, Past Due [Line Items]
Nonaccrual	13,833	11,335	14,832
90+ days and still accruing	6,940	7,799	5,159
Current	3,313,535	2,796,058	2,794,078
Loans, net of unearned income, excluding covered loans	3,368,423	2,841,659	2,833,452
Premium finance receivables | Commercial | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	17,977	11,382	8,848
Premium finance receivables | Commercial | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	16,138	15,085	10,535
Premium finance receivables | Life insurance loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	590	0	0
90+ days and still accruing	0	0	0
Current	4,449,078	4,340,856	4,074,685
Loans, net of unearned income, excluding covered loans	4,487,921	4,373,891	4,118,666
Premium finance receivables | Life insurance loans | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	18,580	8,407	26,770
Premium finance receivables | Life insurance loans | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	19,673	24,628	17,211
Premium finance receivables | PCI - life insurance loans
Financing Receivable, Past Due [Line Items]
Nonaccrual	0	0	0
90+ days and still accruing	0	0	0
Current	146,557	167,903	183,622
Loans, net of unearned income, excluding covered loans	146,557	167,903	183,622
Premium finance receivables | PCI - life insurance loans | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	0	0	0
Premium finance receivables | PCI - life insurance loans | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	0	0	0
Consumer and other
Financing Receivable, Past Due [Line Items]
Nonaccrual	220	348	563
90+ days and still accruing	235	227	286
Current	108,268	119,246	120,397
Loans, net of unearned income, excluding covered loans	109,192	120,641	121,706
Consumer and other | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Past Due	242	87	150
Consumer and other | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Past Due	$ 227	$ 733	$ 310