Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator: [Abstract]
Net income attributable to BOK Financial Corp. shareholders	$ 62,079	$ 110,612
Less: Earnings allocated to participating securities	343	828
Numerator for basic earnings per share – income available to common shareholders	61,736	109,784
Effect of reallocating undistributed earnings of participating securities	0	0
Numerator for diluted earnings per share – income available to common shareholders	$ 61,736	$ 109,784
Denominator: [Abstract]
Weighted average shares outstanding (in shares)	70,513,807	71,926,041
Less: Participating securities included in weighted average shares (in shares)	390,122	538,971
Denominator for basic earnings per common share (in shares)	70,123,685	71,387,070
Dilutive effect of employee stock compensation plans (in shares)	6,481	17,318
Denominator for diluted earnings per common share (in shares)	70,130,166	71,404,388
Basic earnings per share (per share)	$ 0.88	$ 1.54
Diluted earnings per share (per share)	$ 0.88	$ 1.54