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, 2017	Dec. 31, 2016	Jun. 30, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	$ 20,743,332	$ 19,703,172	$ 18,174,655
Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	6,406,289	6,005,422	5,144,533
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	6,402,494	6,196,087	5,848,334
Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	689,483	725,793	760,904
Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	762,810	705,221	653,664
Consumer and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	114,827	122,041	127,378
Commercial, industrial and other | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	4,094,532	3,744,712	3,456,575
Franchise | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	838,394	869,721	289,905
Mortgage warehouse lines of credit | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	234,643	204,225	270,586
Asset-based lending | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	871,906	875,070	842,667
Leases | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	356,604	294,914	268,074
PCI - commercial | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	10,210	16,780	16,726
Construction | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	709,587	610,239	404,905
Land | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	112,153	104,801	105,881
Office | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	887,684	867,674	909,453
Industrial | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	792,791	770,601	766,769
Retail | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	920,494	912,593	897,846
Multi-family | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	814,598	807,624	778,517
Mixed use and other | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,018,950	1,952,175	1,812,665
PCI - commercial real estate | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	146,237	170,380	172,298
Commercial insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,648,386	2,478,581	2,478,280
Life insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	3,492,709	3,220,370	2,869,960
PCI - life insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	226,334	249,657	291,602
Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	20,674,282	19,615,718	18,086,536
Performing | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	6,396,098	5,989,373	5,127,497
Performing | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	6,385,514	6,174,163	5,823,919
Performing | Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	680,001	716,032	752,342
Performing | Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	748,339	692,472	641,251
Performing | Consumer and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	114,325	121,458	126,740
Performing | Commercial, industrial and other | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	4,085,812	3,731,097	3,440,161
Performing | Franchise | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	838,394	869,721	289,905
Performing | Mortgage warehouse lines of credit | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	234,643	204,225	270,586
Performing | Asset-based lending | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	870,970	873,146	842,432
Performing | Leases | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	356,069	294,404	267,687
Performing | PCI - commercial | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	10,210	16,780	16,726
Performing | Construction | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	707,179	607,831	404,232
Performing | Land | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	111,951	104,407	104,156
Performing | Office | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	882,878	863,337	903,179
Performing | Industrial | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	790,598	763,554	756,474
Performing | Retail | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	918,859	911,996	896,930
Performing | Multi-family | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	814,244	806,981	778,427
Performing | Mixed use and other | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,013,568	1,945,677	1,808,223
Performing | PCI - commercial real estate | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	146,237	170,380	172,298
Performing | Commercial insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,632,008	2,455,910	2,453,225
Performing | Life insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	3,491,663	3,216,653	2,869,960
Performing | PCI - life insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	226,334	249,657	291,602
Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	69,050	87,454	88,119
Non-performing | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	10,191	16,049	17,036
Non-performing | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	16,980	21,924	24,415
Non-performing | Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	9,482	9,761	8,562
Non-performing | Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	14,471	12,749	12,413
Non-performing | Consumer and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	502	583	638
Non-performing | Commercial, industrial and other | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	8,720	13,615	16,414
Non-performing | Franchise | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0	0	0
Non-performing | Mortgage warehouse lines of credit | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0	0	0
Non-performing | Asset-based lending | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	936	1,924	235
Non-performing | Leases | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	535	510	387
Non-performing | PCI - commercial | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0	0	0
Non-performing | Construction | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,408	2,408	673
Non-performing | Land | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	202	394	1,725
Non-performing | Office | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	4,806	4,337	6,274
Non-performing | Industrial | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,193	7,047	10,295
Non-performing | Retail | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	1,635	597	916
Non-performing | Multi-family | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	354	643	90
Non-performing | Mixed use and other | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	5,382	6,498	4,442
Non-performing | PCI - commercial real estate | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0	0	0
Non-performing | Commercial insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	16,378	22,671	25,055
Non-performing | Life insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	1,046	3,717	0
Non-performing | PCI - life insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	$ 0	$ 0	$ 0