FAIR VALUE MEASUREMENT - Schedule of Fair Value Hierarchy Measurement (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets:
Fair value of debt securities available for sale	$ 1,003,437	$ 1,072,093
Single family mortgage servicing rights	59,872
Derivative assets	12,587	27,639
Liabilities:
Derivative liabilities	1,118	2,785
Residential mortgage-backed securities
Assets:
Fair value of debt securities available for sale	37,587	51,046
Commercial mortgage-backed securities
Assets:
Fair value of debt securities available for sale	42,738	45,184
Municipal bonds
Assets:
Fair value of debt securities available for sale	545,817	564,703
Corporate debt securities
Assets:
Fair value of debt securities available for sale	14,975	15,222
Agency debentures
Assets:
Fair value of debt securities available for sale		1,846
Recurring
Assets:
Fair value of loans held for sale	182,790	194,643
Fair value of loans held for investment	5,207	7,108
Single family mortgage servicing rights	59,872	49,966
Total assets	1,268,090	1,359,699
Liabilities:
Total liabilities	15,234	24,232
Recurring \| Residential mortgage-backed securities
Assets:
Fair value of debt securities available for sale	37,587	51,046
Recurring \| Commercial mortgage-backed securities
Assets:
Fair value of debt securities available for sale	42,738	45,184
Recurring \| Collateralized mortgage obligations residential
Assets:
Fair value of debt securities available for sale	195,334	234,909
Recurring \| Collateralized mortgage obligations commercial
Assets:
Fair value of debt securities available for sale	143,400	159,183
Recurring \| Municipal bonds
Assets:
Fair value of debt securities available for sale	545,817	564,703
Recurring \| Corporate debt securities
Assets:
Fair value of debt securities available for sale	14,975	15,222
Recurring \| U.S. Treasury securities
Assets:
Fair value of debt securities available for sale	23,586
Recurring \| Agency debentures
Assets:
Fair value of debt securities available for sale		1,846
Recurring \| Eurodollar futures
Liabilities:
Derivative liabilities	14	4
Recurring \| Forward sale commitments
Assets:
Derivative assets	1,100	1,035
Liabilities:
Derivative liabilities	1,069	3,714
Recurring \| Interest rate lock commitments
Assets:
Derivative assets	5,901	17,395
Liabilities:
Derivative liabilities	8	3
Recurring \| Interest rate swaps
Assets:
Derivative assets	9,783	17,459
Liabilities:
Derivative liabilities	14,143	20,511
Level 1 \| Recurring
Assets:
Fair value of loans held for sale	0	0
Fair value of loans held for investment	0	0
Single family mortgage servicing rights	0	0
Total assets	0	0
Liabilities:
Total liabilities	14	4
Level 1 \| Recurring \| Residential mortgage-backed securities
Assets:
Fair value of debt securities available for sale	0	0
Level 1 \| Recurring \| Commercial mortgage-backed securities
Assets:
Fair value of debt securities available for sale	0	0
Level 1 \| Recurring \| Collateralized mortgage obligations residential
Assets:
Fair value of debt securities available for sale	0	0
Level 1 \| Recurring \| Collateralized mortgage obligations commercial
Assets:
Fair value of debt securities available for sale	0	0
Level 1 \| Recurring \| Municipal bonds
Assets:
Fair value of debt securities available for sale	0	0
Level 1 \| Recurring \| Corporate debt securities
Assets:
Fair value of debt securities available for sale	0	0
Level 1 \| Recurring \| U.S. Treasury securities
Assets:
Fair value of debt securities available for sale	0
Level 1 \| Recurring \| Agency debentures
Assets:
Fair value of debt securities available for sale		0
Level 1 \| Recurring \| Eurodollar futures
Liabilities:
Derivative liabilities	14	4
Level 1 \| Recurring \| Forward sale commitments
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Level 1 \| Recurring \| Interest rate lock commitments
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Level 1 \| Recurring \| Interest rate swaps
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Level 2 \| Recurring
Assets:
Fair value of loans held for sale	182,790	194,643
Fair value of loans held for investment	0	0
Single family mortgage servicing rights	0	0
Total assets	1,194,560	1,282,520
Liabilities:
Total liabilities	15,212	24,225
Level 2 \| Recurring \| Residential mortgage-backed securities
Assets:
Fair value of debt securities available for sale	35,115	48,417
Level 2 \| Recurring \| Commercial mortgage-backed securities
Assets:
Fair value of debt securities available for sale	42,738	45,184
Level 2 \| Recurring \| Collateralized mortgage obligations residential
Assets:
Fair value of debt securities available for sale	195,334	234,909
Level 2 \| Recurring \| Collateralized mortgage obligations commercial
Assets:
Fair value of debt securities available for sale	143,400	159,183
Level 2 \| Recurring \| Municipal bonds
Assets:
Fair value of debt securities available for sale	545,817	564,703
Level 2 \| Recurring \| Corporate debt securities
Assets:
Fair value of debt securities available for sale	14,897	15,141
Level 2 \| Recurring \| U.S. Treasury securities
Assets:
Fair value of debt securities available for sale	23,586
Level 2 \| Recurring \| Agency debentures
Assets:
Fair value of debt securities available for sale		1,846
Level 2 \| Recurring \| Eurodollar futures
Liabilities:
Derivative liabilities	0	0
Level 2 \| Recurring \| Forward sale commitments
Assets:
Derivative assets	1,100	1,035
Liabilities:
Derivative liabilities	1,069	3,714
Level 2 \| Recurring \| Interest rate lock commitments
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Level 2 \| Recurring \| Interest rate swaps
Assets:
Derivative assets	9,783	17,459
Liabilities:
Derivative liabilities	14,143	20,511
Level 3 \| Recurring
Assets:
Fair value of loans held for sale	0	0
Fair value of loans held for investment	5,207	7,108
Single family mortgage servicing rights	59,872	49,966
Total assets	73,530	77,179
Liabilities:
Total liabilities	8	3
Level 3 \| Recurring \| Residential mortgage-backed securities
Assets:
Fair value of debt securities available for sale	2,472	2,629
Level 3 \| Recurring \| Commercial mortgage-backed securities
Assets:
Fair value of debt securities available for sale	0	0
Level 3 \| Recurring \| Collateralized mortgage obligations residential
Assets:
Fair value of debt securities available for sale	0	0
Level 3 \| Recurring \| Collateralized mortgage obligations commercial
Assets:
Fair value of debt securities available for sale	0	0
Level 3 \| Recurring \| Municipal bonds
Assets:
Fair value of debt securities available for sale	0	0
Level 3 \| Recurring \| Corporate debt securities
Assets:
Fair value of debt securities available for sale	78	81
Level 3 \| Recurring \| U.S. Treasury securities
Assets:
Fair value of debt securities available for sale	0
Level 3 \| Recurring \| Agency debentures
Assets:
Fair value of debt securities available for sale		0
Level 3 \| Recurring \| Eurodollar futures
Liabilities:
Derivative liabilities	0	0
Level 3 \| Recurring \| Forward sale commitments
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Level 3 \| Recurring \| Interest rate lock commitments
Assets:
Derivative assets	5,901	17,395
Liabilities:
Derivative liabilities	8	3
Level 3 \| Recurring \| Interest rate swaps
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities		$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value of financial and nonfinancial obligations.

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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