Allowance for Loan Losses, Allowance for Losses on Lending-Related Commitments and Impaired Loans (Summary of Recorded Investment Based on Performance of Loans by Class) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 23,820,691	$ 21,640,797
Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	23,707,457	21,550,635
Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	113,234	90,162
Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	7,828,538	6,787,677
Commercial | Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	5,120,096	4,342,505
Commercial | Franchise
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	948,979	847,597
Commercial | Mortgage warehouse lines of credit
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	144,199	194,523
Commercial | Asset-based lending
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,026,056	980,466
Commercial | Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	565,680	413,172
Commercial | PCI - commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	23,528	9,414
Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	7,777,554	6,771,981
Commercial | Performing | Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	5,085,798	4,331,245
Commercial | Performing | Franchise
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	932,928	845,150
Commercial | Performing | Mortgage warehouse lines of credit
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	144,199	194,523
Commercial | Performing | Asset-based lending
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,025,421	978,916
Commercial | Performing | Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	565,680	412,733
Commercial | Performing | PCI - commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	23,528	9,414
Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	50,984	15,696
Commercial | Non-performing | Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	34,298	11,260
Commercial | Non-performing | Franchise
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	16,051	2,447
Commercial | Non-performing | Mortgage warehouse lines of credit
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	0	0
Commercial | Non-performing | Asset-based lending
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	635	1,550
Commercial | Non-performing | Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	0	439
Commercial | Non-performing | PCI - commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	0	0
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	6,933,252	6,580,618
Commercial real estate | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	760,824	745,514
Commercial real estate | Land
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	141,481	126,484
Commercial real estate | Office
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	939,322	894,833
Commercial real estate | Industrial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	902,248	883,019
Commercial real estate | Retail
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	892,478	951,527
Commercial real estate | Multi-family
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	976,560	915,644
Commercial real estate | Mixed use and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	2,205,195	1,935,705
Commercial real estate | PCI - commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	115,144	127,892
Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	6,914,123	6,558,570
Commercial real estate | Performing | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	759,270	742,371
Commercial real estate | Performing | Land
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	141,374	126,296
Commercial real estate | Performing | Office
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	935,693	892,395
Commercial real estate | Performing | Industrial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	901,963	882,208
Commercial real estate | Performing | Retail
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	881,725	939,199
Commercial real estate | Performing | Multi-family
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	976,249	915,644
Commercial real estate | Performing | Mixed use and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	2,202,705	1,932,565
Commercial real estate | Performing | PCI - commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	115,144	127,892
Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	19,129	22,048
Commercial real estate | Non-performing | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,554	3,143
Commercial real estate | Non-performing | Land
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	107	188
Commercial real estate | Non-performing | Office
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	3,629	2,438
Commercial real estate | Non-performing | Industrial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	285	811
Commercial real estate | Non-performing | Retail
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	10,753	12,328
Commercial real estate | Non-performing | Multi-family
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	311	0
Commercial real estate | Non-performing | Mixed use and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	2,490	3,140
Commercial real estate | Non-performing | PCI - commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	0	0
Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	552,343	663,045
Home equity | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	545,196	654,067
Home equity | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	7,147	8,978
Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	1,002,464	832,120
Residential real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	986,081	810,865
Residential real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	16,383	21,255
Premium finance receivables | Commercial insurance loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	2,841,659	2,634,565
Premium finance receivables | Life insurance loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	4,373,891	3,835,790
Premium finance receivables | PCI - life insurance loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	167,903	199,269
Premium finance receivables | Performing | Commercial insurance loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	2,822,525	2,613,160
Premium finance receivables | Performing | Life insurance loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	4,373,891	3,835,790
Premium finance receivables | Performing | PCI - life insurance loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	167,903	199,269
Premium finance receivables | Non-performing | Commercial insurance loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	19,134	21,405
Premium finance receivables | Non-performing | Life insurance loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	0	0
Premium finance receivables | Non-performing | PCI - life insurance loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	0	0
Consumer and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	120,641	107,713
Consumer and other | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	120,184	106,933
Consumer and other | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income	$ 457	$ 780