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		6 Months Ended		12 Months Ended
	Jun. 30, 2016 USD ($) Loan contracts	Jun. 30, 2015 USD ($) Loan contracts	Jun. 30, 2016 USD ($) Loan contracts	Jun. 30, 2015 USD ($) Loan contracts	Jun. 30, 2016 USD ($) Loan	Jun. 30, 2015 USD ($) Loan
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count	2	6	13	9	16	17
Total, Balance	$ 655	$ 1,317	$ 9,378	$ 1,611	$ 9,801	$ 6,093
Subsequent Default, Count | Loan	6	4	8	4
Subsequent Default, Balance	$ 1,413	$ 833	$ 1,614	$ 833
Commercial | Commercial, industrial and other
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count	1	0	2	0	2	1
Total, Balance	$ 275	$ 0	$ 317	$ 0	$ 317	$ 1,461
Subsequent Default, Count | Loan	0	0	0	0
Subsequent Default, Balance	$ 0	$ 0	$ 0	$ 0
Commercial real estate | Office
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count	0	0	1	1	1	1
Total, Balance	$ 0	$ 0	$ 450	$ 169	$ 450	$ 720
Subsequent Default, Count | Loan	1	0	1	0
Subsequent Default, Balance	$ 450	$ 0	$ 450	$ 0
Commercial real estate | Industrial
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count	0	1	6	0	6	2
Total, Balance	$ 0	$ 169	$ 7,921	$ 0	$ 7,921	$ 854
Subsequent Default, Count | Loan	3	0	3	0
Subsequent Default, Balance	$ 725	$ 0	$ 725	$ 0
Commercial real estate | Mixed use and other
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count	0	0	2	0	4	0
Total, Balance	$ 0	$ 0	$ 150	$ 0	$ 351	$ 0
Subsequent Default, Count | Loan	1	0	3	0
Subsequent Default, Balance	$ 16	$ 0	$ 217	$ 0
Residential real estate and other
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Total, Count	1	5	2	8	3	13
Total, Balance	$ 380	$ 1,148	$ 540	$ 1,442	$ 762	$ 3,058
Subsequent Default, Count | Loan	1	4	1	4
Subsequent Default, Balance	$ 222	$ 833	$ 222	$ 833