LOAN PORTFOLIO - Corporation's Commercial Credit Exposure (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 8,996,816	$ 8,858,123	$ 8,695,890
Commercial Portfolio Segment [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	3,854,962	3,750,202
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	1,558,724	1,522,662	1,552,503
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	2,211,731	2,148,111	2,061,773
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	84,507	79,429	$ 79,150
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	11,461	11,151
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	53,384	47,965
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Land [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	19,662	20,313
Special Mention [Member] | Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	170,218	172,260
Special Mention [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	78,472	85,557
Special Mention [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Special Mention [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Special Mention [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Land [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Substandard [Member] | Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	249,975	276,935
Substandard [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	42,887	45,274
Substandard [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	1,869	2,102
Substandard [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Substandard [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Land [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	6,889	7,407
Doubtful [Member] | Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	12,158	1,701
Doubtful [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	877	6,114
Doubtful [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Doubtful [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Doubtful [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Land [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Loss [Member] | Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Loss [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	274	396
Loss [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Loss [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Loss [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Land [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Total Criticized Asset [Member] | Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	432,351	450,896
Total Criticized Asset [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	122,510	137,341
Total Criticized Asset [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	1,869	2,102
Total Criticized Asset [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Total Criticized Asset [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Land [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 6,889	$ 7,407