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	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	$ 39,022	$ 51,113	$ 49,961
Impaired Financing Receivable, Related Allowance	6,836	8,483	6,380
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	51,518	61,914	51,294
Impaired Financing Receivable, Recorded Investment	90,540	113,027	101,255
Impaired Financing Receivable, Unpaid Principal Balance	106,758	132,788	124,249
Impaired Financing Receivable, Average Recorded Investment	94,750	116,642	107,170
Impaired Financing Receivable, Interest Income Recognized	4,066	4,731	6,198
Commercial | Commercial, industrial and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,426	8,580	9,754
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	5,434	9,118	12,498
Impaired Financing Receivable, Related Allowance	1,887	1,865	2,012
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	5,487	8,906	10,123
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	212	381	792
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	12,669	9,142	8,562
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	16,261	11,997	9,915
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	14,745	9,716	9,885
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	717	539	521
Commercial | Asset-based lending
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	234	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	235	0	0
Impaired Financing Receivable, Related Allowance	44	0	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	235	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	7	0	0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	12	8
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	1,573	1,570
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	4	5
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0	66	88
Commercial | Leases
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	375	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	375	0	0
Impaired Financing Receivable, Related Allowance	116	0	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	388	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	14	0	0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0	0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0	0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0	0	0
Commercial real estate | Construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0	0	0
Impaired Financing Receivable, Related Allowance	0	0	0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	0	0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0	0	0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,995	2,054	2,328
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,995	2,055	2,329
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,273	2,034	2,316
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	94	73	113
Commercial real estate | Land
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,620	3,559	4,929
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,620	7,309	8,711
Impaired Financing Receivable, Related Allowance	44	31	41
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	2,670	3,713	5,127
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	80	362	547
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,864	4,114	888
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	8,088	4,874	2,373
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	4,316	4,232	929
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	408	130	90
Commercial real estate | Office
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,697	6,765	5,050
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,361	7,724	6,051
Impaired Financing Receivable, Related Allowance	182	2,162	632
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,722	7,113	5,394
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	79	263	314
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	4,980	4,171	3,500
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	6,243	5,120	4,484
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	4,978	4,243	3,613
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	260	194	237
Commercial real estate | Industrial
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6,855	10,049	8,413
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	7,338	10,542	9,105
Impaired Financing Receivable, Related Allowance	1,388	1,550	1,943
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	7,069	10,662	10,590
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	284	421	565
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,508	2,255	2,217
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	3,827	2,448	2,426
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,574	2,304	2,286
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	200	141	188
Commercial real estate | Retail
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6,605	8,899	8,527
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	6,623	9,596	9,230
Impaired Financing Receivable, Related Allowance	240	381	343
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	6,668	8,906	8,596
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	160	306	386
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	805	3,140	2,757
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	913	3,302	2,925
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	936	3,305	2,897
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	36	104	129
Commercial real estate | Multi-family
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,266	1,199	370
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,266	1,622	370
Impaired Financing Receivable, Related Allowance	8	203	202
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,134	1,210	372
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	29	60	25
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	89	1,330	2,344
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	174	1,635	2,807
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	109	1,522	2,390
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	5	50	117
Commercial real estate | Mixed use and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,437	7,162	7,590
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	5,511	7,345	7,708
Impaired Financing Receivable, Related Allowance	605	1,501	570
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	5,452	7,250	7,681
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	198	224	328
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	5,164	13,788	10,510
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	5,712	16,576	14,060
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	5,300	14,668	11,939
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	236	563	624
Home equity
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,373	547	423
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,457	762	435
Impaired Financing Receivable, Related Allowance	964	239	333
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	2,404	672	351
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	63	25	16
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	6,936	7,818	6,424
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	9,108	8,406	7,987
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	7,736	7,065	5,738
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	320	229	288
Residential real estate
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,942	4,225	4,710
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	6,428	4,326	4,799
Impaired Financing Receivable, Related Allowance	1,166	521	294
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	5,807	4,280	4,618
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	190	130	182
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	11,098	13,788	11,559
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	13,077	15,932	13,979
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	11,125	14,387	11,903
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	445	449	624
Consumer and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	192	128	195
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	192	128	220
Impaired Financing Receivable, Related Allowance	192	30	10
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	194	139	216
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	8	6	12
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	410	302	197
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	520	398	267
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	428	311	201
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	$ 21	$ 15	$ 12