Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator: [Abstract]:
Net income attributable to BOK Financial Corp. shareholders	$ 500,758	$ 445,646	$ 334,644
Less: Earnings allocated to participating securities	3,227	3,737	3,561
Numerator for basic earnings per share - income available to common shareholders	497,531	441,909	331,083
Effect of reallocating undistributed earnings of participating securities	0	1	2
Numerator for diluted earnings per share - income available to common shareholders	$ 497,531	$ 441,910	$ 331,085
Denominator: [Abstract]
Weighted average shares outstanding	71,250,081	67,190,257	65,440,832
Less: Participating securities included in weighted average shares outstanding (in shares)	462,381	561,617	695,468
Denominator for basic earnings per common share (in shares)	70,787,700	66,628,640	64,745,364
Dilutive effect of employee stock compensation plans (in shares)	14,912	33,633	60,920
Denominator for diluted earnings per common share (in shares)	70,802,612	66,662,273	64,806,284
Basic (in dollars per share)	$ 7.03	$ 6.63	$ 5.11
Diluted earnings per share (per share)	$ 7.03	$ 6.63	$ 5.11