Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator: [Abstract]
Net income attributable to BOK Financial Corp. shareholders	$ 110,612	$ 105,562
Less: Earnings allocated to participating securities	828	1,022
Numerator for basic earnings per share – income available to common shareholders	109,784	104,540
Effect of reallocating undistributed earnings of participating securities	0	0
Numerator for diluted earnings per share – income available to common shareholders	$ 109,784	$ 104,540
Denominator: [Abstract]
Weighted average shares outstanding (in shares)	71,926,041	65,479,482
Less: Participating securities included in weighted average shares (in shares)	538,971	632,148
Denominator for basic earnings per common share (in shares)	71,387,070	64,847,334
Dilutive effect of employee stock compensation plans (in shares)	17,318	40,699
Denominator for diluted earnings per common share (in shares)	71,404,388	64,888,033
Basic earnings per share (per share)	$ 1.54	$ 1.61
Diluted earnings per share (per share)	$ 1.54	$ 1.61
Excludes employee stock options with exercise prices greater than current market price.	0	0