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	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	$ 110,612	$ 105,326	$ 80,936
90+ days and still accruing	15,251	18,872	14,216
Current	23,893,423	23,526,168	21,794,020
Loans, net of unearned income, excluding covered loans	24,214,629	23,820,691	22,062,134
60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	19,181	34,176	17,952
30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	176,162	136,149	155,010
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	55,792	50,984	14,007
90+ days and still accruing	2,499	3,313	856
Current	7,884,413	7,737,729	6,991,004
Loans, net of unearned income, excluding covered loans	7,994,191	7,828,538	7,060,871
Commercial | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,787	1,651	771
Commercial | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	49,700	34,861	54,233
Commercial | Commercial, industrial and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	38,858	34,298	10,051
90+ days and still accruing	0	0	0
Current	5,172,214	5,062,729	4,518,760
Loans, net of unearned income, excluding covered loans	5,250,953	5,120,096	4,560,880
Commercial | Commercial, industrial and other | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,787	1,451	594
Commercial | Commercial, industrial and other | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	38,094	21,618	31,475
Commercial | Franchise
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	15,799	16,051	2,401
90+ days and still accruing	0	0	0
Current	863,573	924,190	931,710
Loans, net of unearned income, excluding covered loans	879,906	948,979	935,358
Commercial | Franchise | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0	44
Commercial | Franchise | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	534	8,738	1,203
Commercial | Mortgage warehouse lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	0	0	0
90+ days and still accruing	0	0	0
Current	174,284	144,199	157,699
Loans, net of unearned income, excluding covered loans	174,284	144,199	163,470
Commercial | Mortgage warehouse lines of credit | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0	0
Commercial | Mortgage warehouse lines of credit | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0	5,771
Commercial | Asset-based lending
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	1,135	635	1,194
90+ days and still accruing	0	0	0
Current	1,031,878	1,022,065	963,883
Loans, net of unearned income, excluding covered loans	1,040,834	1,026,056	977,735
Commercial | Asset-based lending | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	200	47
Commercial | Asset-based lending | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	7,821	3,156	12,611
Commercial | Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	0	0	361
90+ days and still accruing	0	0	0
Current	620,088	564,430	410,667
Loans, net of unearned income, excluding covered loans	622,884	565,680	414,198
Commercial | Leases | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0	0
Commercial | Leases | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2,796	1,250	3,170
Commercial | PCI - commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	0	0	0
90+ days and still accruing	2,499	3,313	856
Current	22,376	20,116	8,285
Loans, net of unearned income, excluding covered loans	25,330	23,528	9,230
Commercial | PCI - commercial | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0	86
Commercial | PCI - commercial | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	455	99	3
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	15,933	19,129	21,825
90+ days and still accruing	4,265	6,241	3,107
Current	6,892,823	6,845,490	6,546,556
Loans, net of unearned income, excluding covered loans	6,973,505	6,933,252	6,633,520
Commercial real estate | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	5,612	10,826	3,563
Commercial real estate | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	54,872	51,566	58,469
Commercial real estate | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	1,030	1,554	3,139
90+ days and still accruing	0	0	0
Current	798,266	749,846	802,921
Loans, net of unearned income, excluding covered loans	803,669	760,824	815,636
Commercial real estate | Construction | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	496	0	0
Commercial real estate | Construction | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	3,877	9,424	9,576
Commercial real estate | Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	54	107	182
90+ days and still accruing	0	0	0
Current	143,759	141,097	117,981
Loans, net of unearned income, excluding covered loans	147,701	141,481	122,690
Commercial real estate | Land | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	170	0
Commercial real estate | Land | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	3,888	107	4,527
Commercial real estate | Office
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	4,482	3,629	474
90+ days and still accruing	0	0	0
Current	918,529	929,739	878,206
Loans, net of unearned income, excluding covered loans	926,375	939,322	891,071
Commercial real estate | Office | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	877	925
Commercial real estate | Office | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	3,364	5,077	11,466
Commercial real estate | Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	267	285	1,427
90+ days and still accruing	0	0	0
Current	953,011	885,367	898,867
Loans, net of unearned income, excluding covered loans	964,960	902,248	906,144
Commercial real estate | Industrial | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,039	0	823
Commercial real estate | Industrial | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	10,643	16,596	5,027
Commercial real estate | Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	7,645	10,753	12,274
90+ days and still accruing	0	0	0
Current	879,473	878,106	878,563
Loans, net of unearned income, excluding covered loans	895,267	892,478	895,622
Commercial real estate | Retail | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	1,890	0
Commercial real estate | Retail | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	8,149	1,729	4,785
Commercial real estate | Multi-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	303	311	19
90+ days and still accruing	0	0	0
Current	1,116,220	970,597	931,008
Loans, net of unearned income, excluding covered loans	1,117,385	976,560	931,355
Commercial real estate | Multi-family | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	187	77	0
Commercial real estate | Multi-family | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	675	5,575	328
Commercial real estate | Mixed use and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	2,152	2,490	4,310
90+ days and still accruing	0	0	0
Current	1,987,008	2,192,105	1,937,328
Loans, net of unearned income, excluding covered loans	2,007,487	2,205,195	1,955,456
Commercial real estate | Mixed use and other | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,084	1,617	192
Commercial real estate | Mixed use and other | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	17,243	8,983	13,626
Commercial real estate | PCI - commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	0	0	0
90+ days and still accruing	4,265	6,241	3,107
Current	96,557	98,633	101,682
Loans, net of unearned income, excluding covered loans	110,661	115,144	115,546
Commercial real estate | PCI - commercial real estate | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2,806	6,195	1,623
Commercial real estate | PCI - commercial real estate | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	7,033	4,075	9,134
Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	7,885	7,147	9,828
90+ days and still accruing	0	0	0
Current	515,438	541,960	611,181
Loans, net of unearned income, excluding covered loans	528,448	552,343	626,547
Home equity | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	810	131	1,505
Home equity | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	4,315	3,105	4,033
Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	15,879	16,383	17,214
90+ days and still accruing	1,481	1,292	1,437
Current	1,024,543	976,926	841,416
Loans, net of unearned income, excluding covered loans	1,053,524	1,002,464	869,104
Residential real estate | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	509	1,692	229
Residential real estate | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	11,112	6,171	8,808
Premium finance receivables | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	14,797	11,335	17,342
90+ days and still accruing	6,558	7,799	8,547
Current	2,941,038	2,796,058	2,525,962
Loans, net of unearned income, excluding covered loans	2,988,788	2,841,659	2,576,150
Premium finance receivables | Commercial | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	5,628	11,382	6,543
Premium finance receivables | Commercial | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	20,767	15,085	17,756
Premium finance receivables | Life insurance loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	0	0	0
90+ days and still accruing	168	0	0
Current	4,349,597	4,340,856	3,986,181
Loans, net of unearned income, excluding covered loans	4,389,599	4,373,891	4,002,726
Premium finance receivables | Life insurance loans | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	4,788	8,407	5,125
Premium finance receivables | Life insurance loans | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	35,046	24,628	11,420
Premium finance receivables | PCI - life insurance loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	0	0	0
90+ days and still accruing	0	0	0
Current	165,770	167,903	187,235
Loans, net of unearned income, excluding covered loans	165,770	167,903	187,235
Premium finance receivables | PCI - life insurance loans | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0	0
Premium finance receivables | PCI - life insurance loans | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	0	0
Consumer and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	326	348	720
90+ days and still accruing	280	227	269
Current	119,801	119,246	104,485
Loans, net of unearned income, excluding covered loans	120,804	120,641	105,981
Consumer and other | 60-89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	47	87	216
Consumer and other | 30-59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	$ 350	$ 733	$ 291