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LOANS, LEASES, AND ALLOWANCE FOR CREDIT LOSSES (Summary of Outstanding Loan Balances (Accruing and Nonaccruing) Categorized by Credit Quality Indicators - Prior Year) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Total loans
2024	$ 7,130		$ 7,130		$ 8,437
2023	7,626		7,626		6,729
2022	5,773		5,773		11,321
2021	9,505		9,505		7,007
2020	6,036		6,036		3,912
Prior	9,720		9,720		7,759
Revolving loans amortized cost basis	13,866		13,866		13,581
Revolving loans converted to term loans amortized cost basis	646		646		664
Total loans	60,302		60,302		59,410
Gross charge-offs by year of loan origination
2024	0	$ 0	1	$ 0
2023	1	1	2	10
2022	3	5	5	13
2021	1	0	2	2
2020	3	0	7	0
Prior	2	1	15	6
Revolving loans gross charge-offs	57	7	75	17
Revolving loans converted to term loans gross charge-offs	0	1	0	2
Total	67	15	107	50
Commercial:
Total loans
2024	3,730		3,730		4,715
2023	4,338		4,338		3,552
2022	2,786		2,786		4,551
2021	3,670		3,670		3,558
2020	2,987		2,987		1,911
Prior	4,764		4,764		3,796
Revolving loans amortized cost basis	8,617		8,617		8,630
Revolving loans converted to term loans amortized cost basis	287		287		252
Total loans	31,179		31,179		30,965
Gross charge-offs by year of loan origination
2024	0	0	0	0
2023	1	1	2	3
2022	0	5	2	9
2021	1	0	2	2
2020	3	0	6	0
Prior	1	1	12	4
Revolving loans gross charge-offs	55	4	68	10
Revolving loans converted to term loans gross charge-offs	0	1	0	2
Total	61	12	92	30
Commercial real estate:
Total loans
2024	2,599		2,599		2,451
2023	1,954		1,954		2,078
2022	1,931		1,931		3,361
2021	2,504		2,504		1,521
2020	1,181		1,181		1,067
Prior	2,025		2,025		1,734
Revolving loans amortized cost basis	1,034		1,034		961
Revolving loans converted to term loans amortized cost basis	249		249		304
Total loans	13,477		13,477		13,477
Gross charge-offs by year of loan origination
Total	3	0	4	11
Consumer:
Total loans
2024	801		801		1,271
2023	1,334		1,334		1,099
2022	1,056		1,056		3,409
2021	3,331		3,331		1,928
2020	1,868		1,868		934
Prior	2,931		2,931		2,229
Revolving loans amortized cost basis	4,215		4,215		3,990
Revolving loans converted to term loans amortized cost basis	110		110		108
Total loans	15,646		15,646		14,968
Gross charge-offs by year of loan origination
2024	0	0	0	0
2023	0	0	0	0
2022	0	0	0	0
2021	0	0	0	0
2020	0	0	1	0
Prior	1	0	3	2
Revolving loans gross charge-offs	2	3	7	7
Revolving loans converted to term loans gross charge-offs	0	0	0	0
Total	3	3	11	9
Commercial and industrial | Commercial:
Total loans
2024	2,506		2,506		2,576
2023	2,258		2,258		2,031
2022	1,522		1,522		1,782
2021	1,125		1,125		810
2020	467		467		418
Prior	800		800		738
Revolving loans amortized cost basis	8,352		8,352		8,366
Revolving loans converted to term loans amortized cost basis	192		192		170
Total loans	17,222		17,222		16,891
Gross charge-offs by year of loan origination
2024	0	0	0	0
2023	1	1	2	3
2022	0	4	2	8
2021	1	0	2	2
2020	0	0	3	0
Prior	1	1	12	4
Revolving loans gross charge-offs	55	4	68	10
Revolving loans converted to term loans gross charge-offs	0	1	0	2
Total	58	11	89	29
Owner-occupied | Commercial:
Total loans
2024	828		828		1,412
2023	1,356		1,356		936
2022	776		776		1,723
2021	1,586		1,586		1,755
2020	1,613		1,613		927
Prior	2,791		2,791		2,263
Revolving loans amortized cost basis	263		263		264
Revolving loans converted to term loans amortized cost basis	54		54		53
Total loans	9,267		9,267		9,333
Gross charge-offs by year of loan origination
2024		0		0
2023		0		0
2022		1		1
2021		0		0
2020		0		0
Prior		0		0
Revolving loans gross charge-offs		0		0
Revolving loans converted to term loans gross charge-offs		0		0
Total		1		1
Municipal | Commercial:
Total loans
2024	350		350		617
2023	627		627		502
2022	422		422		939
2021	869		869		965
2020	888		888		553
Prior	1,142		1,142		759
Revolving loans amortized cost basis	2		2		0
Revolving loans converted to term loans amortized cost basis	41		41		29
Total loans	4,341		4,341		4,364
Gross charge-offs by year of loan origination
2024	0		0
2023	0		0
2022	0		0
2021	0		0
2020	3		3
Prior	0		0
Revolving loans gross charge-offs	0		0
Revolving loans converted to term loans gross charge-offs	0		0
Total	3		3
Leasing | Commercial:
Total loans
2024	46		46		110
2023	97		97		83
2022	66		66		107
2021	90		90		28
2020	19		19		13
Prior	31		31		36
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	349		349		377
Gross charge-offs by year of loan origination
2024			0
2023			0
2022			0
2021			0
2020			0
Prior			0
Revolving loans gross charge-offs			0
Revolving loans converted to term loans gross charge-offs			0
Total			0
Term | Commercial real estate:
Total loans
2024	2,255		2,255		2,033
2023	1,415		1,415		1,303
2022	1,335		1,335		2,646
2021	2,297		2,297		1,422
2020	1,180		1,180		1,066
Prior	2,023		2,023		1,725
Revolving loans amortized cost basis	295		295		281
Revolving loans converted to term loans amortized cost basis	208		208		227
Total loans	11,008		11,008		10,703
Gross charge-offs by year of loan origination
2024	0		1	0
2023	0		0	7
2022	3		3	4
2021	0		0	0
2020	0		0	0
Prior	0		0	0
Revolving loans gross charge-offs	0		0	0
Revolving loans converted to term loans gross charge-offs	0		0	0
Total	3		4	11
Construction and land development | Commercial real estate:
Total loans
2024	344		344		418
2023	539		539		775
2022	596		596		715
2021	207		207		99
2020	1		1		1
Prior	2		2		9
Revolving loans amortized cost basis	739		739		680
Revolving loans converted to term loans amortized cost basis	41		41		77
Total loans	2,469		2,469		2,774
1-4 family residential | Consumer:
Total loans
2024	596		596		1,062
2023	968		968		873
2022	926		926		2,967
2021	3,148		3,148		1,886
2020	1,858		1,858		927
Prior	2,927		2,927		2,224
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	10,423		10,423		9,939
Gross charge-offs by year of loan origination
2024			0	0
2023			0	0
2022			0	0
2021			0	0
2020			1	0
Prior			2	1
Revolving loans gross charge-offs			0	0
Revolving loans converted to term loans gross charge-offs			0	0
Total			3	1
Home equity credit line | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	3,738		3,738		3,534
Revolving loans converted to term loans amortized cost basis	110		110		107
Total loans	3,848		3,848		3,641
Gross charge-offs by year of loan origination
2024		0	0	0
2023		0	0	0
2022		0	0	0
2021		0	0	0
2020		0	0	0
Prior		0	0	0
Revolving loans gross charge-offs		1	1	1
Revolving loans converted to term loans gross charge-offs		0	0	0
Total		1	1	1
Construction and other consumer real estate | Consumer:
Total loans
2024	147		147		157
2023	336		336		191
2022	108		108		420
2021	170		170		34
2020	6		6		5
Prior	2		2		3
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	769		769		810
Bankcard and other revolving plans | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	477		477		456
Revolving loans converted to term loans amortized cost basis	0		0		1
Total loans	477		477		457
Gross charge-offs by year of loan origination
2024	0	0	0	0
2023	0	0	0	0
2022	0	0	0	0
2021	0	0	0	0
2020	0	0	0	0
Prior	0	0	0	0
Revolving loans gross charge-offs	2	2	6	6
Revolving loans converted to term loans gross charge-offs	0	0	0	0
Total	2	$ 2	6	6
Other | Consumer:
Total loans
2024	58		58		52
2023	30		30		35
2022	22		22		22
2021	13		13		8
2020	4		4		2
Prior	2		2		2
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	129		129		121
Gross charge-offs by year of loan origination
2024	0		0	0
2023	0		0	0
2022	0		0	0
2021	0		0	0
2020	0		0	0
Prior	1		1	1
Revolving loans gross charge-offs	0		0	0
Revolving loans converted to term loans gross charge-offs	0		0	0
Total	1		1	$ 1
Pass | Commercial and industrial | Commercial:
Total loans
2024	2,491		2,491		2,479
2023	2,136		2,136		1,951
2022	1,453		1,453		1,504
2021	1,014		1,014		759
2020	434		434		387
Prior	749		749		679
Revolving loans amortized cost basis	8,082		8,082		8,043
Revolving loans converted to term loans amortized cost basis	149		149		150
Total loans	16,508		16,508		15,952
Pass | Owner-occupied | Commercial:
Total loans
2024	809		809		1,346
2023	1,323		1,323		907
2022	757		757		1,606
2021	1,457		1,457		1,657
2020	1,506		1,506		900
Prior	2,651		2,651		2,097
Revolving loans amortized cost basis	237		237		234
Revolving loans converted to term loans amortized cost basis	50		50		47
Total loans	8,790		8,790		8,794
Pass | Municipal | Commercial:
Total loans
2024	350		350		604
2023	624		624		498
2022	422		422		939
2021	869		869		960
2020	886		886		553
Prior	1,124		1,124		753
Revolving loans amortized cost basis	2		2		0
Revolving loans converted to term loans amortized cost basis	41		41		29
Total loans	4,318		4,318		4,336
Pass | Leasing | Commercial:
Total loans
2024	46		46		109
2023	95		95		79
2022	63		63		94
2021	78		78		26
2020	18		18		12
Prior	30		30		36
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	330		330		356
Pass | Term | Commercial real estate:
Total loans
2024	1,954		1,954		1,687
2023	1,301		1,301		1,198
2022	1,174		1,174		2,093
2021	1,788		1,788		1,278
2020	1,102		1,102		1,053
Prior	1,951		1,951		1,608
Revolving loans amortized cost basis	268		268		254
Revolving loans converted to term loans amortized cost basis	154		154		175
Total loans	9,692		9,692		9,346
Pass | Construction and land development | Commercial real estate:
Total loans
2024	293		293		361
2023	530		530		701
2022	513		513		445
2021	127		127		4
2020	1		1		1
Prior	2		2		9
Revolving loans amortized cost basis	739		739		680
Revolving loans converted to term loans amortized cost basis	41		41		52
Total loans	2,246		2,246		2,253
Pass | 1-4 family residential | Consumer:
Total loans
2024	595		595		1,062
2023	966		966		870
2022	921		921		2,959
2021	3,135		3,135		1,877
2020	1,844		1,844		925
Prior	2,898		2,898		2,197
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	10,359		10,359		9,890
Pass | Home equity credit line | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	3,702		3,702		3,506
Revolving loans converted to term loans amortized cost basis	106		106		99
Total loans	3,808		3,808		3,605
Pass | Construction and other consumer real estate | Consumer:
Total loans
2024	147		147		157
2023	336		336		191
2022	108		108		420
2021	170		170		34
2020	6		6		5
Prior	2		2		3
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	769		769		810
Pass | Bankcard and other revolving plans | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	474		474		453
Revolving loans converted to term loans amortized cost basis	0		0		1
Total loans	474		474		454
Pass | Other | Consumer:
Total loans
2024	58		58		52
2023	30		30		35
2022	22		22		22
2021	13		13		8
2020	4		4		2
Prior	2		2		2
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	129		129		121
Special Mention | Commercial and industrial | Commercial:
Total loans
2024	10		10		37
2023	58		58		24
2022	7		7		47
2021	2		2		8
2020	11		11		2
Prior	14		14		34
Revolving loans amortized cost basis	87		87		85
Revolving loans converted to term loans amortized cost basis	5		5		5
Total loans	194		194		242
Special Mention | Owner-occupied | Commercial:
Total loans
2024	2		2		38
2023	2		2		0
2022	0		0		38
2021	11		11		31
2020	12		12		2
Prior	24		24		18
Revolving loans amortized cost basis	0		0		18
Revolving loans converted to term loans amortized cost basis	1		1		1
Total loans	52		52		146
Special Mention | Municipal | Commercial:
Total loans
2024	0		0		0
2023	3		3		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	3		3		0
Special Mention | Leasing | Commercial:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		2
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	0		0		2
Special Mention | Term | Commercial real estate:
Total loans
2024	9		9		48
2023	13		13		0
2022	10		10		87
2021	99		99		0
2020	0		0		0
Prior	1		1		5
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	132		132		140
Special Mention | Construction and land development | Commercial real estate:
Total loans
2024	0		0		0
2023	1		1		22
2022	36		36		21
2021	32		32		17
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		25
Total loans	69		69		85
Special Mention | 1-4 family residential | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	0		0		0
Special Mention | Home equity credit line | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	0		0		0
Special Mention | Construction and other consumer real estate | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	0		0		0
Special Mention | Bankcard and other revolving plans | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	0		0		0
Special Mention | Other | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	0		0		0
Accruing Substandard | Commercial and industrial | Commercial:
Total loans
2024	1		1		53
2023	60		60		43
2022	59		59		200
2021	70		70		26
2020	19		19		28
Prior	31		31		21
Revolving loans amortized cost basis	162		162		200
Revolving loans converted to term loans amortized cost basis	11		11		12
Total loans	413		413		583
Accruing Substandard | Owner-occupied | Commercial:
Total loans
2024	11		11		23
2023	24		24		28
2022	17		17		75
2021	112		112		66
2020	93		93		25
Prior	101		101		133
Revolving loans amortized cost basis	24		24		7
Revolving loans converted to term loans amortized cost basis	3		3		5
Total loans	385		385		362
Accruing Substandard | Municipal | Commercial:
Total loans
2024	0		0		10
2023	0		0		4
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	18		18		3
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	18		18		17
Accruing Substandard | Leasing | Commercial:
Total loans
2024	0		0		1
2023	1		1		3
2022	2		2		10
2021	10		10		2
2020	1		1		1
Prior	1		1		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	15		15		17
Accruing Substandard | Term | Commercial real estate:
Total loans
2024	270		270		298
2023	101		101		105
2022	135		135		443
2021	388		388		144
2020	78		78		13
Prior	61		61		102
Revolving loans amortized cost basis	27		27		27
Revolving loans converted to term loans amortized cost basis	54		54		26
Total loans	1,114		1,114		1,158
Accruing Substandard | Construction and land development | Commercial real estate:
Total loans
2024	51		51		57
2023	8		8		52
2022	47		47		249
2021	48		48		78
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	154		154		436
Accruing Substandard | 1-4 family residential | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	1		1		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	1		1		0
Accruing Substandard | Home equity credit line | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	8		8		6
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	8		8		6
Accruing Substandard | Construction and other consumer real estate | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	0		0		0
Accruing Substandard | Bankcard and other revolving plans | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	2		2		2
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	2		2		2
Accruing Substandard | Other | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	0		0		0
Nonaccrual | Commercial and industrial | Commercial:
Total loans
2024	4		4		7
2023	4		4		13
2022	3		3		31
2021	39		39		17
2020	3		3		1
Prior	6		6		4
Revolving loans amortized cost basis	21		21		38
Revolving loans converted to term loans amortized cost basis	27		27		3
Total loans	107		107		114
Nonaccrual | Owner-occupied | Commercial:
Total loans
2024	6		6		5
2023	7		7		1
2022	2		2		4
2021	6		6		1
2020	2		2		0
Prior	15		15		15
Revolving loans amortized cost basis	2		2		5
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	40		40		31
Nonaccrual | Municipal | Commercial:
Total loans
2024	0		0		3
2023	0		0		0
2022	0		0		0
2021	0		0		5
2020	2		2		0
Prior	0		0		3
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	2		2		11
Nonaccrual | Leasing | Commercial:
Total loans
2024	0		0		0
2023	1		1		1
2022	1		1		1
2021	2		2		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	4		4		2
Nonaccrual | Term | Commercial real estate:
Total loans
2024	22		22		0
2023	0		0		0
2022	16		16		23
2021	22		22		0
2020	0		0		0
Prior	10		10		10
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		26
Total loans	70		70		59
Nonaccrual | Construction and land development | Commercial real estate:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	0		0		0
Nonaccrual | 1-4 family residential | Consumer:
Total loans
2024	1		1		0
2023	2		2		3
2022	5		5		8
2021	13		13		9
2020	14		14		2
Prior	28		28		27
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	63		63		49
Nonaccrual | Home equity credit line | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	28		28		22
Revolving loans converted to term loans amortized cost basis	4		4		8
Total loans	32		32		30
Nonaccrual | Construction and other consumer real estate | Consumer:
Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	0		0		0
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	0		0		0
Nonaccrual | Bankcard and other revolving plans | Consumer:
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2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
Revolving loans amortized cost basis	1		1		1
Revolving loans converted to term loans amortized cost basis	0		0		0
Total loans	1		1		1
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Total loans
2024	0		0		0
2023	0		0		0
2022	0		0		0
2021	0		0		0
2020	0		0		0
Prior	0		0		0
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