PORTFOLIO LOANS - Schedule of Activity on the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Activity in the allowance for loan losses
ACL beginning balance	$ 183,334	$ 85,226	$ 83,404	$ 91,740
Day 1 PCD				1,243
Day 2 Provision for Credit Losses	(3,305)		50,308	6,677
Provision for loan losses		2	(2,281)	7,317
Charged-off	(7,448)	(674)	(52,666)	(16,410)
Recoveries	1,600	427	2,508	1,091
ACL ending balance	174,181	84,981	174,181	84,981
CrossFirst
Activity in the allowance for loan losses
Day 1 PCD			100,783
Day 2 Provision for Credit Losses			42,433
Commercial loans \| C&I and other commercial
Activity in the allowance for loan losses
ACL beginning balance	68,578	20,286	21,589	21,256
Day 1 PCD				824
Day 2 Provision for Credit Losses	(4,768)
Provision for loan losses		715	(23,008)	13,958
Charged-off	(5,753)	(202)	(39,054)	(15,433)
Recoveries	1,379	210	1,692	404
ACL ending balance	59,436	21,009	59,436	21,009
Commercial loans \| C&I and other commercial \| CrossFirst
Activity in the allowance for loan losses
Day 1 PCD			75,569
Day 2 Provision for Credit Losses			22,648
Commercial loans \| CRE
Activity in the allowance for loan losses
ACL beginning balance	70,935	35,104	32,301	35,465
Day 1 PCD				322
Day 2 Provision for Credit Losses	1,323
Provision for loan losses		(1,158)	14,300	(1,882)
Charged-off	(1,438)	(215)	(12,607)	(315)
Recoveries	24	4	158	145
ACL ending balance	70,844	33,735	70,844	33,735
Commercial loans \| CRE \| CrossFirst
Activity in the allowance for loan losses
Day 1 PCD			21,588
Day 2 Provision for Credit Losses			15,104
Commercial loans \| Real estate construction
Activity in the allowance for loan losses
ACL beginning balance	13,072	3,722	3,345	5,163
Day 1 PCD				0
Day 2 Provision for Credit Losses	(880)
Provision for loan losses		39	3,731	(1,449)
Charged-off	0	0	0	0
Recoveries	1	10	94	57
ACL ending balance	12,193	3,771	12,193	3,771
Commercial loans \| Real estate construction \| CrossFirst
Activity in the allowance for loan losses
Day 1 PCD			2,112
Day 2 Provision for Credit Losses			2,911
Retail loans \| CRE
Activity in the allowance for loan losses
ACL beginning balance	29,042	23,729	23,711	26,298
Day 1 PCD				96
Day 2 Provision for Credit Losses	739
Provision for loan losses		120	2,833	(2,624)
Charged-off	(53)	(32)	(172)	(159)
Recoveries	115	162	413	368
ACL ending balance	29,843	23,979	29,843	23,979
Retail loans \| CRE \| CrossFirst
Activity in the allowance for loan losses
Day 1 PCD			1,430
Day 2 Provision for Credit Losses			1,628
Retail loans \| Retail other
Activity in the allowance for loan losses
ACL beginning balance	1,707	2,385	2,458	3,558
Day 1 PCD				1
Day 2 Provision for Credit Losses	281
Provision for loan losses		286	(137)	(686)
Charged-off	(204)	(225)	(833)	(503)
Recoveries	81	41	151	117
ACL ending balance	$ 1,865	$ 2,487	1,865	$ 2,487
Retail loans \| Retail other \| CrossFirst
Activity in the allowance for loan losses
Day 1 PCD			84
Day 2 Provision for Credit Losses			$ 142

Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal), Excluding Business Acquisition

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
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- Definition

Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
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-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
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-Section 50
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-Publisher FASB
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- Definition

Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
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- Definition

Amount, excluding accrued interest, of allowance for credit loss at acquisition date of financing receivable purchased with credit deterioration. Excludes net investment in lease.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
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