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 expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - New Accounting Pronouncements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity attributable to parent	$ (907,245)	$ (897,207)		$ (945,534)	$ (1,012,308)
Reserve for unfunded loan commitments	57,649	81,030	$ 57,649
Allowance for credit losses - unfunded loan commitments			4,064
Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments	61,713	84,213		66,814	53,049
Commercial \| Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			22,353
Commercial \| Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			5,941
Commercial \| Multifamily
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			11,405
Commercial \| SBA
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			3,120
Commercial \| Construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			3,906
Consumer \| Single family residential mortgage
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			10,486
Consumer \| Other consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			438
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity attributable to parent	(127,733)	$ (110,179)		(140,952)	(144,343)
Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Transfer of loans to held-for-sale	6,400
Stockholders' equity attributable to parent	4,503
Reserve for unfunded loan commitments			7,609
Allowance for credit losses - unfunded loan commitments			(1,226)
Impact of ASC 326 Adoption \| Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments	6,383			$ 0	$ 0
Impact of ASC 326 Adoption \| Commercial \| Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			662
Impact of ASC 326 Adoption \| Commercial \| Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			4,847
Impact of ASC 326 Adoption \| Commercial \| Multifamily
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			1,809
Impact of ASC 326 Adoption \| Commercial \| SBA
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			388
Impact of ASC 326 Adoption \| Commercial \| Construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			103
Impact of ASC 326 Adoption \| Consumer \| Single family residential mortgage
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			(420)
Impact of ASC 326 Adoption \| Consumer \| Other consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			220
Impact of ASC 326 Adoption \| Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity attributable to parent	$ 4,503
As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			65,258
Allowance for credit losses - unfunded loan commitments			2,838
As Reported Under ASC 326 \| Commercial \| Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			23,015
As Reported Under ASC 326 \| Commercial \| Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			10,788
As Reported Under ASC 326 \| Commercial \| Multifamily
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			13,214
As Reported Under ASC 326 \| Commercial \| SBA
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			3,508
As Reported Under ASC 326 \| Commercial \| Construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			4,009
As Reported Under ASC 326 \| Consumer \| Single family residential mortgage
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			10,066
As Reported Under ASC 326 \| Consumer \| Other consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserve for unfunded loan commitments			$ 658