LOAN PORTFOLIO - Commercial Credit Exposure - Credit RiskProfile Based on Creditworthiness Category (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 8,858,123	$ 8,850,476	$ 8,886,873
Commercial And Industrial Sector [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	2,148,111	2,083,253
Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	79,429	111,397	124,951
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	1,522,662	1,614,972
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	3,750,202	3,809,622
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	2,148,111	2,083,253	2,180,455
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	47,965	76,556
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	20,313	26,931
Residential Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	3,163,208	3,290,957	$ 3,296,031
Residential Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	11,151	7,910
Substandard [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	276,935	257,503
Substandard [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	45,274	154,416
Substandard [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	35,100
Substandard [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	7,407	15,971
Substandard [Member] | Residential Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	2,102	1,987
Doubtful [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	1,701	4,166
Doubtful [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	6,114	3,854
Doubtful [Member] | Commercial Portfolio Segment [Member] | Construction Loans [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	490
Doubtful [Member] | Residential Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Loss [Member] | Commercial Real Estate Portfolio Segment [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	396	676
Loss [Member] | Commercial Portfolio Segment [Member] | Construction Loans [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
Loss [Member] | Residential Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	0
Total Adversely Classified [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	278,636	261,669
Total Adversely Classified [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	51,784	158,946
Total Adversely Classified [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	0	35,100
Total Adversely Classified [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member] | Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	7,407	16,461
Total Adversely Classified [Member] | Residential Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 2,102	$ 1,987