Allowance for Loan Losses, Allowance for Losses on Lending-Related Commitments and Impaired Loans (Summary of Impaired Loans by Loan Class) (Detail) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	$ 29,037	$ 42,968	$ 33,146
Impaired Financing Receivable, Related Allowance	5,633	6,611	6,377
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	50,281	53,008	57,370
Impaired Financing Receivable, Recorded Investment	79,318	95,976	90,516
Impaired Financing Receivable, Unpaid Principal Balance	90,876	114,113	103,046
Impaired Financing Receivable, Average Recorded Investment	84,874	97,879	105,423
Impaired Financing Receivable, Interest Income Recognized	2,261	2,860	5,485
Commercial | Commercial, industrial and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,969	10,253	2,601
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	3,006	12,866	2,617
Impaired Financing Receivable, Related Allowance	1,499	3,280	1,079
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	3,061	10,172	2,649
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	83	375	134
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	6,815	10,092	12,534
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	7,785	10,950	14,704
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	7,285	10,045	14,944
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	213	328	948
Commercial | Asset-based lending
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	511	0	233
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	512	0	235
Impaired Financing Receivable, Related Allowance	293	0	26
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	704	0	235
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	21	0	10
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	425	0	1,691
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	425	0	2,550
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	764	0	8,467
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	16	0	377
Commercial | Leases
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,504	387	2,441
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,508	387	2,443
Impaired Financing Receivable, Related Allowance	235	128	107
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	2,578	390	2,561
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	62	10	128
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	852	0	873
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	852	0	873
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	879	0	939
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	26	0	56
Commercial real estate | Construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	7,632	0	5,302
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	7,632	0	5,302
Impaired Financing Receivable, Related Allowance	957	0	86
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	7,665	0	5,368
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	165	0	164
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,504	2,677	4,003
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,504	2,677	4,003
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,534	2,693	4,161
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	33	77	81
Commercial real estate | Land
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,750	4,538	1,283
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,750	4,538	1,283
Impaired Financing Receivable, Related Allowance	7	18	1
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,750	4,592	1,303
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	32	83	47
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,375	2,979	3,034
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	2,472	7,492	3,503
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,380	3,001	3,371
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	56	254	142
Commercial real estate | Office
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,314	2,401	2,687
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,418	3,059	2,697
Impaired Financing Receivable, Related Allowance	32	176	324
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,318	2,427	2,797
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	44	70	137
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,973	6,967	3,994
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	5,074	8,715	5,921
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	4,076	7,107	4,002
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	131	227	323
Commercial real estate | Industrial
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0	7,369	5,207
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0	7,773	5,843
Impaired Financing Receivable, Related Allowance	0	1,514	1,810
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	7,552	7,804
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0	195	421
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,193	3,966	2,129
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	3,622	5,093	2,436
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	4,328	4,326	2,828
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	190	168	274
Commercial real estate | Retail
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,582	7,007	1,750
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,631	7,024	1,834
Impaired Financing Receivable, Related Allowance	130	264	170
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,596	7,064	2,039
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	40	95	101
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,188	1,122	0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,273	1,122	0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,188	1,129	0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	51	27	0
Commercial real estate | Multi-family
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,513	1,274	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,513	1,274	0
Impaired Financing Receivable, Related Allowance	27	15	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,518	1,066	0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	28	18	0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	89	90	1,903
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	174	174	1,987
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	89	119	1,825
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	4	3	84
Commercial real estate | Mixed use and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,455	3,040	3,812
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,531	3,162	4,010
Impaired Financing Receivable, Related Allowance	302	109	592
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,478	3,063	4,038
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	35	73	195
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	7,761	5,435	6,815
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	9,299	5,960	7,388
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	8,494	5,498	6,912
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	239	159	397
Home equity
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,901	1,349	1,961
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,950	1,511	1,873
Impaired Financing Receivable, Related Allowance	1,296	477	1,233
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,920	1,443	1,969
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	35	30	75
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	7,732	7,213	8,033
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	11,260	9,674	10,483
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	8,906	8,356	8,830
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	258	219	475
Residential real estate
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,815	5,230	5,752
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	6,090	5,840	6,327
Impaired Financing Receivable, Related Allowance	764	625	849
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	5,731	5,289	5,816
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	118	123	261
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	15,044	12,051	11,983
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	17,068	14,180	14,124
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	15,203	11,997	12,041
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	368	308	622
Consumer and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	91	120	117
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	93	148	121
Impaired Financing Receivable, Related Allowance	91	5	100
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	96	123	131
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	2	4	7
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	330	416	378
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	434	494	489
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	333	427	393
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	$ 11	$ 14	$ 26