Allowance for Loan Losses, Allowance for Losses on Lending-Related Commitments and Impaired Loans (Summary of TDRs Subsequent Default Under the Restructured Terms) (Detail) $ in Thousands		3 Months Ended				12 Months Ended
		Mar. 31, 2016 USD ($) contracts Loan		Mar. 31, 2015 USD ($) contracts Loan		Mar. 31, 2016 USD ($) Loan		Mar. 31, 2015 USD ($) Loan
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count		11	[1],[2]	3	[1],[2]	20	[3],[4]	18	[3],[4]
Total, Balance		$ 8,723	[1],[2]	$ 294	[1],[2]	$ 10,463	[3],[4]	$ 7,017	[3],[4]
Subsequent Default, Count | Loan	[3],[5]	7		7
Subsequent Default, Balance	[3],[5]	$ 1,392		$ 2,048
Commercial | Commercial, industrial and other
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count		1	[1],[2]	0	[1],[2]	1	[3],[4]	1	[3],[4]
Total, Balance		$ 42	[1],[2]	$ 0	[1],[2]	$ 42	[3],[4]	$ 1,461	[3],[4]
Subsequent Default, Count | Loan	[3],[5]	0		0
Subsequent Default, Balance	[3],[5]	$ 0		$ 0
Commercial real estate | Office
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count		1	[1],[2]	0	[1],[2]	1	[3],[4]	2	[3],[4]
Total, Balance		$ 450	[1],[2]	$ 0	[1],[2]	$ 450	[3],[4]	$ 1,510	[3],[4]
Subsequent Default, Count | Loan	[3],[5]	1		1
Subsequent Default, Balance	[3],[5]	$ 450		$ 790
Commercial real estate | Industrial
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count		6	[1],[2]	0	[1],[2]	7	[3],[4]	1	[3],[4]
Total, Balance		$ 7,921	[1],[2]	$ 0	[1],[2]	$ 8,090	[3],[4]	$ 685	[3],[4]
Subsequent Default, Count | Loan	[3],[5]	3		0
Subsequent Default, Balance	[3],[5]	$ 725		$ 0
Commercial real estate | Multi-family
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count | Loan	[3],[4]					0		1
Total, Balance	[3],[4]					$ 0		$ 181
Subsequent Default, Count | Loan	[3],[5]	0		1
Subsequent Default, Balance	[3],[5]	$ 0		$ 181
Commercial real estate | Mixed use and other
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count		2	[1],[2]	0	[1],[2]	4	[3],[4]	4	[3],[4]
Total, Balance		$ 150	[1],[2]	$ 0	[1],[2]	$ 351	[3],[4]	$ 1,049	[3],[4]
Subsequent Default, Count | Loan	[3],[5]	3		3
Subsequent Default, Balance	[3],[5]	$ 217		$ 816
Residential real estate and other
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count		1	[1],[2]	3	[1],[2]	7	[3],[4]	9	[3],[4]
Total, Balance		$ 160	[1],[2]	$ 294	[1],[2]	$ 1,530	[3],[4]	$ 2,131	[3],[4]
Subsequent Default, Count | Loan	[3],[5]	0		2
Subsequent Default, Balance	[3],[5]	$ 0		$ 261

[1] Balances represent the recorded investment in the loan at the time of the restructuring.

[2] TDRs may have more than one modification representing a concession. As such, TDRs during the period may be represented in more than one of the categories noted above.

[3] Balances represent the recorded investment in the loan at the time of the restructuring.

[4] Total TDRs represent all loans restructured in TDRs during the previous twelve months from the date indicated.

[5] TDRs considered to be in payment default are over 30 days past-due subsequent to the restructuring.