Allowance for Loan Losses, Allowance for Losses on Lending-Related Commitments and Impaired Loans (Summary of Performance by Loan Class) (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	$ 18,174,655	$ 17,118,117	$ 15,513,650
Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	18,086,536	17,034,060	15,437,096
Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	88,119	84,057	76,554
Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	5,144,533	4,713,909	4,330,344
Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	5,127,497	4,700,656	4,324,950
Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	17,036	13,253	5,394
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	5,848,334	5,529,289	4,850,590
Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	5,823,919	5,502,644	4,826,706
Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	24,415	26,645	23,884
Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	760,904	784,675	712,350
Home equity | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	752,342	777,827	706,655
Home equity | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	8,562	6,848	5,695
Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	653,664	607,451	503,015
Residential real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	641,251	595,408	486,384
Residential real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	12,413	12,043	16,631
Consumer and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	127,378	146,376	119,468
Consumer and other | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	126,740	145,963	119,078
Consumer and other | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	638	413	390
Commercial, industrial and other | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	3,456,575	3,258,528	2,858,130
Commercial, industrial and other | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	3,440,161	3,245,818	2,853,706
Commercial, industrial and other | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	16,414	12,710	4,424
Franchise | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	289,905	245,228	228,599
Franchise | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	289,905	245,228	227,694
Franchise | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0	0	905
Mortgage warehouse lines of credit | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	270,586	222,806	213,797
Mortgage warehouse lines of credit | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	270,586	222,806	213,797
Mortgage warehouse lines of credit | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0	0	0
Asset-based lending | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	842,667	742,684	832,455
Asset-based lending | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	842,432	742,676	832,455
Asset-based lending | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	235	8	0
Leases | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	268,074	226,074	187,630
Leases | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	267,687	225,539	187,565
Leases | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	387	535	65
PCI - commercial | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	16,726	18,589	9,733
PCI - commercial | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	16,726	18,589	9,733
PCI - commercial | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0	0	0
Construction | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	404,905	358,660	307,145
Construction | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	404,232	358,354	307,126
Construction | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	673	306	19
Land | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	105,881	78,417	87,837
Land | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	104,156	76,666	85,802
Land | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	1,725	1,751	2,035
Office | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	909,453	863,001	754,817
Office | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	903,179	858,382	747,756
Office | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	6,274	4,619	7,061
Industrial | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	766,769	727,648	627,407
Industrial | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	756,474	718,084	624,839
Industrial | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	10,295	9,564	2,568
Retail | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	897,846	868,399	749,991
Retail | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	896,930	866,639	747,639
Retail | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	916	1,760	2,352
Multi-family | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	778,517	742,349	668,448
Multi-family | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	778,427	740,395	666,718
Multi-family | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	90	1,954	1,730
Mixed use and other | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	1,812,665	1,732,816	1,592,122
Mixed use and other | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	1,808,223	1,726,125	1,584,003
Mixed use and other | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	4,442	6,691	8,119
PCI - commercial real estate | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	172,298	157,999	62,823
PCI - commercial real estate | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	172,298	157,999	62,823
PCI - commercial real estate | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0	0	0
Commercial insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,478,280	2,374,921	2,460,408
Commercial insurance loans | Premium finance receivables | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,453,225	2,350,066	2,436,199
Commercial insurance loans | Premium finance receivables | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	25,055	24,855	24,209
Life insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,869,960	2,593,204	2,153,155
Life insurance loans | Premium finance receivables | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,869,960	2,593,204	2,152,804
Life insurance loans | Premium finance receivables | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0	0	351
PCI - life insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	291,602	368,292	384,320
PCI - life insurance loans | Premium finance receivables | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	291,602	368,292	384,320
PCI - life insurance loans | Premium finance receivables | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	$ 0	$ 0	$ 0