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		3 Months Ended		12 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	[1]	$ 50,710	$ 48,610	$ 49,961
Impaired Financing Receivable, Related Allowance		7,775	6,199	6,380
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		45,400	63,794	51,294
Impaired Financing Receivable, Recorded Investment	[2]	96,110	112,404	101,255
Impaired Financing Receivable, Unpaid Principal Balance		114,793	136,169	124,249
Impaired Financing Receivable, Average Recorded Investment		96,369	113,693	107,170
Impaired Financing Receivable, Interest Income Recognized		1,463	1,588	6,198
Commercial | Commercial, industrial and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		9,711	7,230	9,754
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		12,905	7,830	12,498
Impaired Financing Receivable, Related Allowance		2,309	1,795	2,012
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		9,527	7,465	10,123
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized		207	92	792
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		7,802	4,630	8,562
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		8,591	7,595	9,915
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		8,090	4,647	9,885
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized		116	125	521
Commercial | Asset-based lending
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		3	0	8
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		1,567	0	1,570
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		5	0	5
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized		22	0	88
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		2,296	2,645	2,328
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		2,296	2,645	2,329
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		2,296	2,645	2,316
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized		28	30	113
Commercial real estate | Land
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		5,577	4,475	4,929
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		9,358	8,090	8,711
Impaired Financing Receivable, Related Allowance		49	29	41
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		5,583	4,734	5,127
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized		142	127	547
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		2,112	5,134	888
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		2,852	5,868	2,373
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		2,116	5,137	929
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized		28	62	90
Commercial real estate | Office
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		3,688	8,354	5,050
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		4,688	11,053	6,051
Impaired Financing Receivable, Related Allowance		363	598	632
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		3,701	8,399	5,394
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized		57	131	314
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		7,172	6,890	3,500
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		8,548	6,965	4,484
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		7,323	6,971	3,613
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized		110	77	237
Commercial real estate | Industrial
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		8,325	1,402	8,413
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		9,065	1,487	9,105
Impaired Financing Receivable, Related Allowance		1,872	559	1,943
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		8,382	1,406	10,590
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized		115	20	565
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		3,692	2,772	2,217
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		3,910	3,134	2,426
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		3,686	2,837	2,286
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized		67	55	188
Commercial real estate | Retail
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		7,757	10,259	8,527
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		7,775	12,286	9,230
Impaired Financing Receivable, Related Allowance		296	371	343
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		7,785	10,294	8,596
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized		83	128	386
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		1,800	5,053	2,757
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		2,499	9,130	2,925
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		1,806	5,315	2,897
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized		25	105	129
Commercial real estate | Multi-family
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		1,477	2,266	370
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		1,477	2,363	370
Impaired Financing Receivable, Related Allowance		128	241	202
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		1,050	2,273	372
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized		11	26	25
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		92	777	2,344
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		175	1,199	2,807
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		148	778	2,390
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized		2	13	117
Commercial real estate | Mixed use and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		4,753	7,891	7,590
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		4,900	10,041	7,708
Impaired Financing Receivable, Related Allowance		293	1,449	570
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		4,761	7,907	7,681
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized		58	116	328
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		3,802	17,479	10,510
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		4,377	17,723	14,060
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		3,886	17,688	11,939
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized		58	185	624
Home equity
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		3,508	2,807	423
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		3,559	2,962	435
Impaired Financing Receivable, Related Allowance		1,695	948	333
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		3,508	2,809	351
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized		25	29	16
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		5,857	5,072	6,424
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		6,974	6,771	7,987
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		5,962	5,126	5,738
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized		92	70	288
Residential real estate
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		5,726	3,728	4,710
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		5,957	3,934	4,799
Impaired Financing Receivable, Related Allowance		700	183	294
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		5,743	3,724	4,618
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized		61	45	182
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		10,433	13,159	11,559
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		12,692	14,644	13,979
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		10,481	13,190	11,903
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized		148	145	624
Consumer and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment		188	198	195
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance		215	200	220
Impaired Financing Receivable, Related Allowance		70	26	10
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment		190	203	216
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized		3	4	12
Impaired Financing Receivable, with No Related Allowance, Recorded Investment		339	183	197
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance		413	249	267
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		340	145	201
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized		$ 5	$ 3	$ 12

[1] These impaired loans require an allowance for loan losses because the estimated fair value of the loans or related collateral is less than the recorded investment in the loans.

[2] Impaired loans are considered by the Company to be non-accrual loans, TDRs or loans with principal and/or interest at risk, even if the loan is current with all payments of principal and interest.