Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator: [Abstract]
Net income attributable to BOK Financial Corp. shareholders	$ 137,563	$ 114,372	$ 248,175	$ 219,934
Less: Earnings allocated to participating securities	850	956	1,678	1,978
Numerator for basic earnings per share – income available to common shareholders	136,713	113,416	246,497	217,956
Effect of reallocating undistributed earnings of participating securities	0	1	0	1
Numerator for diluted earnings per share – income available to common shareholders	$ 136,713	$ 113,417	$ 246,497	$ 217,957
Denominator: [Abstract]
Weighted average shares outstanding (in shares)	71,327,928	65,448,035	71,625,332	65,463,671
Less: Participating securities included in weighted average shares (in shares)	440,865	546,060	489,918	589,104
Denominator for basic earnings per common share (in shares)	70,887,063	64,901,975	71,135,414	64,874,567
Dilutive effect of employee stock compensation plans (in shares)	14,970	35,251	16,144	37,985
Denominator for diluted earnings per common share (in shares)	70,902,033	64,937,226	71,151,558	64,912,552
Basic earnings per share (per share)	$ 1.93	$ 1.75	$ 3.47	$ 3.36
Diluted earnings per share (per share)	$ 1.93	$ 1.75	$ 3.46	$ 3.36
Excludes employee stock options with exercise prices greater than current market price.	0	0	0	0