LOANS HELD FOR INVESTMENT - Loan Restructuring and Effect on Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	$ 155,139	$ 196,362
Impact of adopting ASC 326	137,700
Provision (release) for credit losses	74,045	11,820
Ending balance	292,774	183,732
Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	2,370	3,592
Provision (release) for credit losses	2,062	(95)
Ending balance	5,253	3,331
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member]
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	39,194	55,581
Provision (release) for credit losses	14,167	121
Ending balance	33,971	53,430
Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member]
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	15,198	32,546
Provision (release) for credit losses	8,391	(5,009)
Ending balance	38,310	22,321
Entity Loan Modification Program [Member]
Financing Receivable, Troubled Debt Restructuring [Abstract]
Beginning Balance of TDRs	487,997	582,647
New TDRs loan splits	23,125	25,459
Paid-off and partial payments	(9,982)	(13,022)
Ending balance of TDRs	497,295	589,795
Entity Loan Modification Program [Member] \| Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Abstract]
Beginning Balance of TDRs	4,321
Ending balance of TDRs	4,275
Entity Loan Modification Program [Member] \| Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member]
Financing Receivable, Troubled Debt Restructuring [Abstract]
Beginning Balance of TDRs	74,979
Ending balance of TDRs	74,332
Entity Loan Modification Program [Member] \| Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member]
Financing Receivable, Troubled Debt Restructuring [Abstract]
Beginning Balance of TDRs	66,849
Ending balance of TDRs	82,719
Entity Loan Modification Program [Member] \| Ab Note Restructure Workout Strategy [Member]
Financing Receivable, Troubled Debt Restructuring [Abstract]
Beginning Balance of TDRs	51,228	33,840
New TDRs loan splits	0	20,059
Paid-off and partial payments	(322)	(331)
Ending balance of TDRs	50,906	53,568
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	3,530	473
Provision (release) for credit losses	(87)	487
Ending balance	3,117	960
Entity Loan Modification Program [Member] \| Ab Note Restructure Workout Strategy [Member] \| Accounting Standards Update 2016-13 [Member] \| Cumulative Effect Period Of Adoption Adjustment [Member]
Loans And Leases Receivable Disclosure [Abstract]
Impact of adopting ASC 326	(326)	0
Entity Loan Modification Program [Member] \| Ab Note Restructure Workout Strategy [Member] \| Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Abstract]
Beginning Balance of TDRs	1,883	2,431
New TDRs loan splits	0	0
Paid-off and partial payments	(25)	(71)
Ending balance of TDRs	1,858	2,360
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	0	0
Provision (release) for credit losses	0	0
Ending balance	0	0
Entity Loan Modification Program [Member] \| Ab Note Restructure Workout Strategy [Member] \| Commercial Portfolio Segment [Member] \| Construction Loans [Member] \| Accounting Standards Update 2016-13 [Member] \| Cumulative Effect Period Of Adoption Adjustment [Member]
Loans And Leases Receivable Disclosure [Abstract]
Impact of adopting ASC 326	0	0
Entity Loan Modification Program [Member] \| Ab Note Restructure Workout Strategy [Member] \| Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member]
Financing Receivable, Troubled Debt Restructuring [Abstract]
Beginning Balance of TDRs	22,749	3,003
New TDRs loan splits	0	20,059
Paid-off and partial payments	(97)	(30)
Ending balance of TDRs	22,652	23,032
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	3,516	0
Provision (release) for credit losses	15	611
Ending balance	3,116	611
Entity Loan Modification Program [Member] \| Ab Note Restructure Workout Strategy [Member] \| Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| Accounting Standards Update 2016-13 [Member] \| Cumulative Effect Period Of Adoption Adjustment [Member]
Loans And Leases Receivable Disclosure [Abstract]
Impact of adopting ASC 326	(415)	0
Entity Loan Modification Program [Member] \| Ab Note Restructure Workout Strategy [Member] \| Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member]
Financing Receivable, Troubled Debt Restructuring [Abstract]
Beginning Balance of TDRs	26,596	28,406
New TDRs loan splits	0	0
Paid-off and partial payments	(200)	(230)
Ending balance of TDRs	26,396	28,176
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	14	473
Provision (release) for credit losses	(102)	(124)
Ending balance	1	349
Entity Loan Modification Program [Member] \| Ab Note Restructure Workout Strategy [Member] \| Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member] \| Accounting Standards Update 2016-13 [Member] \| Cumulative Effect Period Of Adoption Adjustment [Member]
Loans And Leases Receivable Disclosure [Abstract]
Impact of adopting ASC 326	$ 89	$ 0

Recorded investment in loans that were modified under troubled debt restructurings during the period.

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Repayments related to Trouble Debt Restructuring Loans.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount of increase (decrease) in allowance for credit loss on financing receivable.

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Amount of financing receivable modified as troubled debt restructuring.

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Amount of expense related to estimated loss from loan and lease transactions.

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