Consolidated Statements of Earnings (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Interest revenue [Abstract]
Loans	$ 293,332	$ 210,694	$ 573,204	$ 398,785
Residential mortgage loans held for sale	1,754	2,333	3,417	4,177
Trading securities	15,498	12,988	34,193	20,726
Investment securities	2,905	3,663	6,939	7,520
Available for sale securities	59,880	47,427	116,711	93,386
Fair value option securities	7,503	3,927	12,740	8,746
Restricted equity securities	6,516	5,408	12,861	10,525
Interest-bearing cash and cash equivalents	3,432	7,740	6,829	15,722
Total interest revenue	390,820	294,180	766,894	559,587
Interest expense [Abstract]
Deposits	43,183	20,963	80,600	39,182
Borrowed funds	58,404	32,607	115,214	58,056
Subordinated debentures	3,801	2,048	7,546	4,051
Total interest expense	105,388	55,618	203,360	101,289
Net interest revenue	285,432	238,562	563,534	458,298
Provision for credit losses	5,000	0	13,000	(5,000)
Net interest revenue after provision for credit losses	280,432	238,562	550,534	463,298
Total fees and commissions	176,108	157,258	336,660	316,872
Other gains (losses), net	3,480	4,578	6,456	3,286
Gain (loss) on derivatives, net	11,150	(3,057)	15,817	(8,742)
Gain (loss) on fair value option securities, net	9,853	(3,341)	19,518	(20,905)
Change in fair value of mortgage servicing rights	(29,555)	1,723	(50,221)	22,929
Gain (loss) on available for sale securities, net	1,029	(762)	1,105	(1,052)
Total other operating revenue	172,065	156,399	329,335	312,388
Other operating expense [Abstract]
Personnel	160,342	138,947	329,570	278,894
Business promotion	10,142	7,686	18,016	13,696
Charitable contributions to BOKF Foundation	1,000	0	1,000	0
Professional fees and services	13,002	14,978	29,141	25,178
Net occupancy and equipment	26,880	22,761	56,401	46,807
Insurance	6,454	6,245	11,293	12,838
Data processing and communications	29,735	27,739	61,184	55,556
Printing, postage and supplies	4,107	4,011	8,992	8,100
Net losses and operating expenses of repossessed assets	580	2,722	2,576	10,427
Amortization of intangible assets	5,138	1,386	10,329	2,686
Mortgage banking costs	11,545	12,890	21,451	23,039
Other expense	8,212	7,111	14,341	13,685
Total other operating expense	277,137	246,476	564,294	490,906
Net income before taxes	175,360	148,485	315,575	284,780
Federal and state income taxes	37,580	33,330	67,530	64,278
Net income	137,780	115,155	248,045	220,502
Net income attributable to non-controlling interests	217	783	(130)	568
Net income attributable to BOK Financial Corporation shareholders	$ 137,563	$ 114,372	$ 248,175	$ 219,934
Earnings per share: [Abstract]
Basic	$ 1.93	$ 1.75	$ 3.47	$ 3.36
Diluted	$ 1.93	$ 1.75	$ 3.46	$ 3.36
Average shares used in computation: [Abstract]
Basic	70,887,063	64,901,975	71,135,414	64,874,567
Diluted	70,902,033	64,937,226	71,151,558	64,912,552
Dividends declared per share	$ 0.50	$ 0.45	$ 1.00	$ 0.90
Brokerage and trading revenue [Member]
Total fees and commissions	$ 40,526	$ 26,488	$ 72,143	$ 57,136
Transaction card revenue [Member]
Total fees and commissions	21,915	20,975	42,653	41,965
Fiduciary and asset management revenue [Member]
Total fees and commissions	45,025	41,692	88,383	83,524
Deposit service charges and fees [Member]
Total fees and commissions	28,074	27,834	56,317	54,994
Mortgage banking revenue [Member]
Total fees and commissions	28,131	26,346	51,965	52,371
Other revenue [Member]
Total fees and commissions	$ 12,437	$ 13,923	$ 25,199	$ 26,882