LOANS HELD FOR INVESTMENT - Loan Restructuring and Effect on Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
	Jan. 01, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	$ 155,139	$ 292,774	$ 155,139	$ 183,732	$ 155,139	$ 196,362
Impact of adopting ASC 326					164,200
Charges to the provision for loan losses		36,408	74,000	12,534	110,453	24,354
Ending balance		319,297	292,774	172,011	319,297	172,011
Accounting Standards Update 2016-13 [Member]
Loans And Leases Receivable Disclosure [Abstract]
Ending balance	236,304
Accounting Standards Update 2016-13 [Member] | Cumulative Effect Period Of Adoption Adjustment [Member]
Loans And Leases Receivable Disclosure [Abstract]
Impact of adopting ASC 326	(434)
Ending balance	81,165
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	2,370	5,253	2,370	3,331	2,370	3,592
Charges to the provision for loan losses		2,601		(542)	4,663	(637)
Ending balance		7,800	5,253	3,026	7,800	3,026
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Accounting Standards Update 2016-13 [Member]
Loans And Leases Receivable Disclosure [Abstract]
Ending balance	3,167
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]
Ending balance	797
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	39,194	33,971	39,194	53,430	39,194	55,581
Charges to the provision for loan losses		15,439		4,541	29,606	4,662
Ending balance		49,435	33,971	46,373	49,435	46,373
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | Accounting Standards Update 2016-13 [Member]
Loans And Leases Receivable Disclosure [Abstract]
Ending balance	19,888
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]
Ending balance	(19,306)
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	15,198	38,310	15,198	22,321	15,198	32,546
Charges to the provision for loan losses		(5)		(594)	8,386	(5,603)
Ending balance		38,310	38,310	21,644	38,310	21,644
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member] | Accounting Standards Update 2016-13 [Member]
Loans And Leases Receivable Disclosure [Abstract]
Ending balance	29,929
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]
Ending balance	14,731
Entity Loan Modification Program [Member]
Financing Receivable, Troubled Debt Restructuring [Abstract]
Beginning Balance of TDRs	487,997	497,295	487,997	589,795	487,997	582,647
New TDRs loans splits		5,421		6,961	28,546	32,420
Increases to existing TDRs		3,508		347	3,611	1,522
Paid-off and partial payments		(8,812)		(9,344)	(18,794)	(22,366)
Ending balance of TDRs		496,207	497,295	582,389	496,207	582,389
Entity Loan Modification Program [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Abstract]
Beginning Balance of TDRs	4,321		4,321		4,321
Ending balance of TDRs		4,296			4,296
Entity Loan Modification Program [Member] | Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable, Troubled Debt Restructuring [Abstract]
Beginning Balance of TDRs	74,979		74,979		74,979
Ending balance of TDRs		72,249			72,249
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		66,849		66,849
Ending balance of TDRs		84,854			84,854
Entity Loan Modification Program [Member] | Ab Note Restructure Workout Strategy [Member]
Financing Receivable, Troubled Debt Restructuring [Abstract]
Beginning Balance of TDRs	51,228	50,906	51,228	53,568	51,228	33,840
New TDRs loans splits					0	20,059
Increases to existing TDRs		405		0	405	0
Paid-off and partial payments		(53)		(352)	(375)	(683)
Ending balance of TDRs		51,258	50,906	53,216	51,258	53,216
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	3,530	3,117	3,530	960	3,530	473
Charges to the provision for loan losses		967		619	880	1,106
Ending balance		4,084	3,117	1,579	4,084	1,579
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	1,858	1,883	2,360	1,883	2,431
New TDRs loans splits					0	0
Increases to existing TDRs		34		0	34	0
Paid-off and partial payments		0		(71)	(25)	(142)
Ending balance of TDRs		1,892	1,858	2,289	1,892	2,289
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	0	0	0	0	0	0
Charges to the provision for loan losses		0		0	0	0
Ending balance		0	0	0	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	22,652	22,749	23,032	22,749	3,003
New TDRs loans splits					0	20,059
Increases to existing TDRs		0		0	0	0
Paid-off and partial payments		(53)		(92)	(150)	(122)
Ending balance of TDRs		22,599	22,652	22,940	22,599	22,940
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	3,516	3,116	3,516	611	3,516	0
Charges to the provision for loan losses		530		650	545	1,261
Ending balance		3,646	3,116	1,261	3,646	1,261
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	26,396	26,596	28,176	26,596	28,406
New TDRs loans splits					0	0
Increases to existing TDRs		371		0	371	0
Paid-off and partial payments		0		(189)	(200)	(419)
Ending balance of TDRs		26,767	26,396	27,987	26,767	27,987
Loans And Leases Receivable Disclosure [Abstract]
Beginning balance	$ 14	1	14	349	14	473
Charges to the provision for loan losses		437		(31)	335	(155)
Ending balance		$ 438	$ 1	$ 318	438	318
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