Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator: [Abstract]
Net income attributable to BOK Financial Corp. shareholders	$ 85,649	$ 74,277	$ 262,152	$ 182,642
Less: Earnings allocated to participating securities	888	916	2,817	2,275
Numerator for basic earnings per share – income available to common shareholders	84,761	73,361	259,335	180,367
Effect of reallocating undistributed earnings of participating securities	1	1	2	1
Numerator for diluted earnings per share – income available to common shareholders	$ 84,762	$ 73,362	$ 259,337	$ 180,368
Denominator: [Abstract]
Weighted average shares outstanding (in shares)	65,423,258	65,895,430	65,432,313	66,031,497
Less: Participating securities included in weighted average shares (in shares)	680,436	810,038	702,922	822,723
Denominator for basic earnings per common share (in shares)	64,742,822	65,085,392	64,729,391	65,208,774
Dilutive effect of employee stock compensation plans (in shares)	62,350	72,449	64,502	54,792
Denominator for diluted earnings per common share (in shares)	64,805,172	65,157,841	64,793,893	65,263,566
Basic earnings per share (per share)	$ 1.31	$ 1.13	$ 4.01	$ 2.77
Diluted earnings per share (per share)	$ 1.31	$ 1.13	$ 4.00	$ 2.76
Excludes employee stock options with exercise prices greater than current market price.	0	0	0	0