Consolidated Statements of Earnings (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Interest revenue [Abstract]
Loans	$ 215,438	$ 293,332	$ 458,656	$ 573,204
Residential mortgage loans held for sale	2,140	1,754	3,263	3,417
Trading Securities	11,407	15,498	23,167	34,193
Investment securities	3,000	2,905	6,121	6,939
Available for sale securities	68,297	59,880	138,017	116,711
Fair value option securities	4,110	7,503	15,818	12,740
Restricted equity securities	1,880	6,516	7,774	12,861
Interest-bearing cash and cash equivalents	112	3,432	2,505	6,829
Total interest revenue	306,384	390,820	655,321	766,894
Interest expense [Abstract]
Deposits	17,745	43,183	63,904	80,600
Borrowed funds	6,996	58,404	44,781	115,214
Subordinated debentures	3,539	3,801	7,172	7,546
Total interest expense	28,280	105,388	115,857	203,360
Net interest revenue	278,104	285,432	539,464	563,534
Provision for credit losses	135,321	5,000	229,092	13,000
Net interest revenue after provision for credit losses	142,783	280,432	310,372	550,534
Total fees and commissions	213,680	176,108	406,404	336,660
Other gains (losses), net	6,768	3,480	(3,973)	6,456
Gain on derivatives, net	21,885	11,150	40,305	15,817
Gain (loss) on fair value option securities, net	(14,459)	9,853	53,934	19,518
Change in fair value of mortgage servicing rights	(761)	(29,555)	(89,241)	(50,221)
Gain on available for sale securities, net	5,580	1,029	5,583	1,105
Total other operating revenue	232,693	172,065	413,012	329,335
Other operating expense [Abstract]
Personnel	176,235	160,342	332,416	329,570
Business promotion	1,935	10,142	8,150	18,016
Contributions to BOKF Foundation	3,000	1,000	3,000	1,000
Professional fees and services	12,161	13,002	25,109	29,141
Net occupancy and equipment	30,675	26,880	56,736	56,401
Insurance	5,156	6,454	10,136	11,293
Data processing and communications	32,942	29,735	65,685	61,184
Printing, postage and supplies	3,502	4,107	7,774	8,992
Net losses and operating expenses of repossessed assets	1,766	580	3,297	2,576
Amortization of intangible assets	5,190	5,138	10,284	10,329
Mortgage banking costs	15,598	11,545	26,143	21,451
Other expense	7,227	8,212	15,281	14,341
Total other operating expense	295,387	277,137	564,011	564,294
Net income before taxes	80,089	175,360	159,373	315,575
Federal and state income taxes	15,803	37,580	33,103	67,530
Net income	64,286	137,780	126,270	248,045
Net income (loss) attributable to non-controlling interests	(407)	217	(502)	(130)
Net income attributable to BOK Financial Corporation shareholders	$ 64,693	$ 137,563	$ 126,772	$ 248,175
Dividends declared per share	$ 0.51	$ 0.50	$ 1.02	$ 1.00
Earnings Per Share [Abstract]
Basic	0.92	1.93	1.80	3.47
Diluted	$ 0.92	$ 1.93	$ 1.80	$ 3.46
Average shares used in computation: [Abstract]
Basic	69,876,043	70,887,063	69,999,865	71,135,414
Diluted	69,877,467	70,902,033	70,003,817	71,151,558
Brokerage and trading revenue [Member]
Total fees and commissions	$ 62,022	$ 40,526	$ 112,801	$ 72,143
Transaction card revenue [Member]
Total fees and commissions	22,940	21,915	44,821	42,653
Fiduciary and asset management revenue [Member]
Total fees and commissions	41,257	45,025	85,715	88,383
Deposit service charges and fees [Member]
Total fees and commissions	22,046	28,074	48,176	56,317
Mortgage banking revenue [Member]
Total fees and commissions	53,936	28,131	91,103	51,965
Other revenue [Member]
Total fees and commissions	$ 11,479	$ 12,437	$ 23,788	$ 25,199