Consolidated Statements of Earnings (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest revenue [Abstract]
Loans	$ 215,977	$ 286,694	$ 674,633	$ 859,898
Residential mortgage loans held for sale	1,585	1,891	4,848	5,308
Trading securities	8,723	14,452	31,890	48,645
Investment securities	2,939	3,221	9,060	10,160
Available for sale securities	62,369	67,633	200,386	184,344
Fair value option securities	1,986	10,708	17,804	23,448
Restricted equity securities	913	7,558	8,687	20,419
Interest-bearing cash and cash equivalents	167	3,050	2,672	9,879
Total interest revenue	294,659	395,207	949,980	1,162,101
Interest expense [Abstract]
Deposits	14,658	46,917	78,562	127,517
Borrowed funds	4,856	65,381	49,637	180,595
Subordinated debentures	3,395	3,813	10,567	11,359
Total interest expense	22,909	116,111	138,766	319,471
Net interest revenue	271,750	279,096	811,214	842,630
Provision for credit losses	0	12,000	229,092	25,000
Net interest revenue after provision for credit losses	271,750	267,096	582,122	817,630
Total fees and commissions	222,865	186,119	629,269	522,779
Other gains, net	6,265	4,544	2,292	11,000
Gain on derivatives, net	2,354	3,778	42,659	19,595
Gain (loss) on fair value option securities, net	(754)	4,597	53,180	24,115
Change in fair value of mortgage servicing rights	3,441	(12,593)	(85,800)	(62,814)
Gain (loss) on available for sale securities, net	(12)	5	5,571	1,110
Total other operating revenue	234,159	186,450	647,171	515,785
Other operating expense [Abstract]
Personnel	179,860	162,573	512,276	492,143
Business promotion	2,633	8,859	10,783	26,875
Charitable contributions to BOKF Foundation	0	0	3,000	1,000
Professional fees and services	14,074	12,312	39,183	41,453
Net occupancy and equipment	28,111	27,558	84,847	83,959
Insurance	5,848	4,220	15,984	15,513
Data processing and communications	34,751	31,915	100,436	93,099
Printing, postage and supplies	3,482	3,825	11,256	12,817
Net losses and operating expenses of repossessed assets	6,244	1,728	9,541	4,304
Amortization of intangible assets	5,071	5,064	15,355	15,393
Mortgage banking costs	15,803	14,975	41,946	36,426
Other expense	5,388	6,263	20,669	20,604
Total other operating expense	301,265	279,292	865,276	843,586
Net income before taxes	204,644	174,254	364,017	489,829
Federal and state income taxes	50,552	32,396	83,655	99,926
Net income	154,092	141,858	280,362	389,903
Net income (loss) attributable to non-controlling interests	58	(373)	(444)	(503)
Net income attributable to BOK Financial Corporation shareholders	$ 154,034	$ 142,231	$ 280,806	$ 390,406
Dividends declared per share	$ 0.51	$ 0.50	$ 1.53	$ 1.50
Earnings Per Share [Abstract]
Basic	2.19	2.00	3.99	5.47
Diluted	$ 2.19	$ 2.00	$ 3.99	$ 5.47
Average shares used in computation: [Abstract]
Basic	69,877,866	70,596,307	69,958,944	70,953,544
Diluted	69,879,290	70,609,924	69,962,053	70,968,845
Brokerage and trading revenue [Member]
Total fees and commissions	$ 69,526	$ 43,840	$ 182,327	$ 115,983
Transaction card revenue [Member]
Total fees and commissions	23,465	22,015	68,286	64,668
Fiduciary and asset management revenue [Member]
Total fees and commissions	39,931	43,621	125,646	132,004
Deposit service charges and fees [Member]
Total fees and commissions	24,286	28,837	72,462	85,154
Mortgage banking revenue [Member]
Total fees and commissions	51,959	30,180	143,062	82,145
Other revenue [Member]
Total fees and commissions	$ 13,698	$ 17,626	$ 37,486	$ 42,825