LOANS AND ALLOWANCE FOR CREDIT LOSSES - Allowance for Loan Losses (Detail) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended		12 Months Ended
	Jan. 01, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 57,649		$ 57,649		$ 57,649
Provision for (reversal of) credit losses		$ 11,826	15,761	$ (1,900)	27,587	$ 198
Balance at end of period	$ 57,649	90,370			$ 90,370		$ 57,649
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member				us-gaap:AccountingStandardsUpdate201613Member		us-gaap:AccountingStandardsUpdate201613Member
Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 61,713	82,131	61,713	68,093	$ 61,713	66,814	$ 66,814
Charge-offs		0		(2,451)	(2,076)	(3,514)
Recoveries		608		76	958	320
Net (charge-offs) recoveries		608		(2,375)	(1,118)	(3,194)
Provision for (reversal of) credit losses		11,826		(1,900)	27,587	198
Balance at end of period		94,565	82,131	63,818	94,565	63,818	61,713
Impact of adopting ASU 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at end of period	7,609
Impact of adopting ASU 2016-13 | Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	6,383		6,383		6,383	0	0
Balance at end of period							6,383
Allowance for Loan Losses
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	57,649	78,243	57,649	63,885	57,649	62,192	62,192
Charge-offs		0		(2,451)	(2,076)	(3,514)
Recoveries		608		76	958	320
Net (charge-offs) recoveries		608		(2,375)	(1,118)	(3,194)
Provision for (reversal of) credit losses		11,519		(1,987)	26,230	525
Balance at end of period		90,370	78,243	59,523	90,370	59,523	57,649
Allowance for Loan Losses | Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	57,649	78,243	57,649	63,885	57,649	62,192	62,192
Charge-offs		0		(2,451)	(2,076)	(3,514)
Recoveries		608		76	958	320
Net (charge-offs) recoveries		608		(2,375)	(1,118)	(3,194)
Provision for (reversal of) credit losses		11,519		(1,987)	26,230	525
Balance at end of period		90,370	78,243	59,523	90,370	59,523	57,649
Allowance for Loan Losses | Impact of adopting ASU 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	7,609		7,609		7,609
Balance at end of period							7,609
Allowance for Loan Losses | Impact of adopting ASU 2016-13 | Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	7,609		7,609		7,609	0	0
Balance at end of period							7,609
Reserve for Unfunded Loan Commitments | Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	4,064	3,888	4,064	4,208	4,064	4,622	4,622
Charge-offs		0		0	0	0
Recoveries		0		0	0	0
Net (charge-offs) recoveries		0		0	0	0
Provision for (reversal of) credit losses		307		87	1,357	(327)
Balance at end of period		$ 4,195	3,888	$ 4,295	4,195	4,295	4,064
Reserve for Unfunded Loan Commitments | Impact of adopting ASU 2016-13 | Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ (1,226)		$ (1,226)		$ (1,226)	$ 0	0
Balance at end of period							$ (1,226)