Consolidated Statements of Earnings (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Interest revenue [Abstract]
Loans	$ 286,694	$ 218,732	$ 859,898	$ 617,517
Residential mortgage loans held for sale	1,891	2,151	5,308	6,328
Trading securities	14,452	17,295	48,645	38,021
Investment securities	3,221	3,598	10,160	11,118
Available for sale securities	67,633	48,917	184,344	142,303
Fair value option securities	10,708	3,881	23,448	12,627
Restricted equity securities	7,558	5,232	20,419	15,757
Interest-bearing cash and cash equivalents	3,050	3,441	9,879	19,163
Total interest revenue	395,207	303,247	1,162,101	862,834
Interest expense [Abstract]
Deposits	46,917	24,535	127,517	63,717
Borrowed funds	65,381	35,804	180,595	93,860
Subordinated debentures	3,813	2,025	11,359	6,076
Total interest expense	116,111	62,364	319,471	163,653
Net interest revenue	279,096	240,883	842,630	699,181
Provision for credit losses	12,000	4,000	25,000	(1,000)
Net interest revenue after provision for credit losses	267,096	236,883	817,630	700,181
Total fees and commissions	186,119	166,197	522,779	483,069
Other gains, net	4,544	2,754	11,000	6,040
Gain (loss) on derivatives, net	3,778	(2,847)	19,595	(11,589)
Gain (loss) on fair value option securities, net	4,597	(4,385)	24,115	(25,290)
Change in fair value of mortgage servicing rights	(12,593)	5,972	(62,814)	28,901
Gain (loss) on available for sale securities, net	5	250	1,110	(802)
Total other operating revenue	186,450	167,941	515,785	480,329
Other operating expense [Abstract]
Personnel	162,573	143,531	492,143	422,425
Business promotion	8,859	7,620	26,875	21,316
Charitable contributions to BOKF Foundation	0	0	1,000	0
Professional fees and services	12,312	13,209	41,453	38,387
Net occupancy and equipment	27,558	23,394	83,959	70,201
Insurance	4,220	6,232	15,513	19,070
Data processing and communications	31,915	31,665	93,099	87,221
Printing, postage and supplies	3,825	3,837	12,817	11,937
Net losses and operating expenses of repossessed assets	1,728	4,044	4,304	14,471
Amortization of intangible assets	5,064	1,603	15,393	4,289
Mortgage banking costs	14,975	11,741	36,426	34,780
Other expense	6,263	5,741	20,604	19,426
Total other operating expense	279,292	252,617	843,586	743,523
Net income before taxes	174,254	152,207	489,829	436,987
Federal and state income taxes	32,396	34,662	99,926	98,940
Net income	141,858	117,545	389,903	338,047
Net income (loss) attributable to non-controlling interests	(373)	289	(503)	857
Net income attributable to BOK Financial Corporation shareholders	$ 142,231	$ 117,256	$ 390,406	$ 337,190
Earnings per share: [Abstract]
Basic	$ 2.00	$ 1.79	$ 5.47	$ 5.15
Diluted	$ 2.00	$ 1.79	$ 5.47	$ 5.15
Average shares used in computation: [Abstract]
Basic	70,596,307	64,901,095	70,953,544	64,883,319
Diluted	70,609,924	64,934,351	70,968,845	64,919,728
Dividends declared per share	$ 0.50	$ 0.50	$ 1.50	$ 1.40
Brokerage and trading revenue [Member]
Total fees and commissions	$ 43,840	$ 23,086	$ 115,983	$ 80,222
Transaction card revenue [Member]
Total fees and commissions	22,015	21,396	64,668	63,361
Fiduciary and asset management revenue [Member]
Total fees and commissions	43,621	57,514	132,004	141,038
Deposit service charges and fees [Member]
Total fees and commissions	28,837	27,765	85,154	82,760
Mortgage banking revenue [Member]
Total fees and commissions	30,180	23,536	82,145	75,907
Other revenue [Member]
Total fees and commissions	$ 17,626	$ 12,900	$ 42,825	$ 39,781