PORTFOLIO LOANS - Schedule of Activity on the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Activity in the allowance for loan losses
ACL beginning balance	$ 195,210	$ 91,562	$ 83,404	$ 91,740
Day 1 PCD		1,243		1,243
Day 2 Provision for Credit Losses	1,005		51,293	6,268
Provision for loan losses		2,277	1,024	7,315
Charged-off	(13,383)	(10,276)	(45,218)	(15,736)
Recoveries	502	420	908	664
ACL ending balance	183,334	85,226	183,334	85,226
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	89,304	26,207	21,589	21,256
Day 1 PCD		824		824
Day 2 Provision for Credit Losses	(18,863)
Provision for loan losses		3,118	(18,240)	13,243
Charged-off	(2,080)	(10,013)	(33,301)	(15,231)
Recoveries	217	150	313	194
ACL ending balance	68,578	20,286	68,578	20,286
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	68,478	33,505	32,301	35,465
Day 1 PCD		322		322
Day 2 Provision for Credit Losses	13,370
Provision for loan losses		1,140	12,977	(724)
Charged-off	(10,916)	(4)	(11,169)	(100)
Recoveries	3	141	134	141
ACL ending balance	70,935	35,104	70,935	35,104
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	8,689	4,713	3,345	5,163
Day 1 PCD		0		0
Day 2 Provision for Credit Losses	4,300
Provision for loan losses		(997)	4,611	(1,488)
Charged-off	0	0	0	0
Recoveries	83	6	93	47
ACL ending balance	13,072	3,722	13,072	3,722
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	26,399	24,281	23,711	26,298
Day 1 PCD		96		96
Day 2 Provision for Credit Losses	2,597
Provision for loan losses		(651)	2,094	(2,744)
Charged-off	(119)	(75)	(119)	(127)
Recoveries	165	78	298	206
ACL ending balance	29,042	23,729	29,042	23,729
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	2,340	2,856	2,458	3,558
Day 1 PCD		1		1
Day 2 Provision for Credit Losses	(399)
Provision for loan losses		(333)	(418)	(972)
Charged-off	(268)	(184)	(629)	(278)
Recoveries	34	45	70	76
ACL ending balance	$ 1,707	$ 2,385	1,707	$ 2,385
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
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

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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
-Subparagraph (e)
-Publisher FASB
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- Definition

Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. 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
-Subparagraph (d)
-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
-SubTopic 20
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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
-SubTopic 20
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