Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator: [Abstract]
Net income attributable to BOK Financial Corp. shareholders	$ 154,034	$ 142,231	$ 280,806	$ 390,406
Less: Earnings allocated to participating securities	938	875	1,678	2,553
Numerator for basic earnings per share – income available to common shareholders	153,096	141,356	279,128	387,853
Effect of reallocating undistributed earnings of participating securities	0	1	0	1
Numerator for diluted earnings per share – income available to common shareholders	$ 153,096	$ 141,357	$ 279,128	$ 387,854
Denominator: [Abstract]
Weighted average shares outstanding (in shares)	70,306,233	71,033,405	70,375,628	71,425,855
Less: Participating securities included in weighted average shares (in shares)	428,367	437,098	416,684	472,311
Denominator for basic earnings per common share (in shares)	69,877,866	70,596,307	69,958,944	70,953,544
Dilutive effect of employee stock compensation plans (in shares)	1,424	13,617	3,109	15,301
Denominator for diluted earnings per common share (in shares)	69,879,290	70,609,924	69,962,053	70,968,845
Basic earnings per share	$ 2.19	$ 2.00	$ 3.99	$ 5.47
Diluted earnings per share	$ 2.19	$ 2.00	$ 3.99	$ 5.47
Excludes employee stock options with exercise prices greater than current market price.	19,227	0	0	0