Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Cash Flows From Operating Activities: [Abstract]
Net income	$ 577,978	$ 523,553	$ 531,133
Adjustments to reconcile net income to net cash provided by (used in) operating activities: [Abstract]
Provision for credit losses	2,000	18,000	46,000
Change in fair value of mortgage servicing rights due to market changes	13,227	(18,437)	3,115
Change in fair value of mortgage servicing rights due to principal payments	29,875	30,807	27,343
Net unrealized losses (gains) from derivative contracts	89,536	(173,247)	133,118
Share-based compensation	22,703	22,883	16,350
Depreciation and amortization	110,206	105,306	109,893
Net amortization of discounts and premiums	(52,129)	(45,069)	(19,985)
Net losses (gains) on financial instruments and other losses (gains), net	(45,718)	(33,898)	(26,162)
Net loss (gain) on mortgage loans held for sale	(8,764)	(7,625)	4,483
Mortgage loans originated for sale	(839,158)	(812,263)	(666,391)
Proceeds from sale of mortgage loans held for sale	830,758	800,376	679,389
Capitalized mortgage servicing rights	(13,066)	(14,976)	(12,141)
Charitable contributions to BOKF Foundation	0	13,610	0
Change in trading and fair value option securities	(577,958)	297,198	(453,340)
Change in receivables	(61,528)	321,945	(316,819)
Change in other assets	111,816	106,972	89,930
Change in other liabilities	549,842	295,319	(79,733)
Net cash provided by (used in) operating activities	739,620	1,430,454	66,183
Cash Flows From Investing Activities: [Abstract]
Proceeds from maturities or redemptions of investment securities	230,688	224,077	268,263
Proceeds from maturities or redemptions of available-for-sale securities	2,220,270	2,138,581	1,558,160
Purchases of investment securities	0	0	(2,504)
Purchases of available-for-sale securities	(2,826,054)	(3,467,059)	(2,951,422)
Proceeds from sales of available-for-sale securities	305,729	839,352	834,704
Change in amount receivable on unsettled available-for-sale securities transactions	(8,351)	100,758	(86,110)
Loans originated, net of principal collected	(1,494,638)	(195,624)	(1,349,900)
Net payments or proceeds on derivative asset contracts	(34,704)	12,204	154,602
Proceeds from sale of BOKF Insurance	0	0	32,601
Net change in restricted equity securities			123,448
Net change in restricted equity securities	181,421	16,921
Proceeds from disposition of assets	68,282	25,147	39,708
Purchases of assets	(164,389)	(171,589)	(165,918)
Net cash provided by (used in) investing activities	(1,521,746)	(477,232)	(1,791,264)
Cash Flows From Financing Activities: [Abstract]
Net change in demand deposits, transaction deposits and savings accounts	1,140,103	3,648,141	(2,011,184)
Net change in time deposits	103,673	523,388	1,550,180
Net change in other borrowed funds	(133,685)	(4,526,879)	1,802,549
Repayment of subordinated debentures	(132,166)	0	0
Issuance of subordinated debentures, net of issuance costs	396,568	0	0
Change in amount due on unsettled security purchases	31,448	(180,074)	190,085
Issuance of common and treasury stock, net	(6,558)	(3,764)	(4,941)
Net change in derivative margin accounts	161,894	(81,284)	631,433
Net payments or proceeds on derivative liability contracts	4,962	(13,477)	(166,275)
Repurchase of common stock	(413,208)	(89,856)	(176,819)
Dividends paid	(147,504)	(142,981)	(143,398)
Net cash provided by (used in) financing activities	1,005,527	(866,786)	1,671,630
Net increase (decrease) in cash and cash equivalents	223,401	86,436	(53,451)
Cash and cash equivalents at beginning of period	1,434,701	1,348,265	1,401,716
Cash and cash equivalents at end of period	1,658,102	1,434,701	1,348,265
Supplemental Cash Flow Information: [Abstract]
Cash paid for interest	1,205,437	1,428,059	1,044,950
Cash paid for federal taxes	80,950	83,000	152,400
Cash paid for state taxes	13,277	17,512	21,516
Net loans and bank premises transferred to repossessed real estate and other assets	167	462	787
Residential mortgage loans guaranteed by U.S. government agencies that became eligible for repurchase during the period	48,361	25,558	14,466
Conveyance of other real estate owned guaranteed by U.S. government agencies	5,674	3,848	5,534
Right-of-use assets obtained in exchange for operating lease liabilities	$ 8,471	$ 19,100	$ 71,865