Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator: [Abstract]
Net income attributable to BOK Financial Corp. shareholders	$ 114,372	$ 88,147	$ 219,934	$ 176,503
Less: Earnings allocated to participating securities	956	926	1,978	1,929
Numerator for basic earnings per share – income available to common shareholders	113,416	87,221	217,956	174,574
Effect of reallocating undistributed earnings of participating securities	1	1	1	1
Numerator for diluted earnings per share – income available to common shareholders	$ 113,417	$ 87,222	$ 217,957	$ 174,575
Denominator: [Abstract]
Weighted average shares outstanding (in shares)	65,448,035	65,416,274	65,463,671	65,436,909
Less: Participating securities included in weighted average shares (in shares)	546,060	686,522	589,104	714,165
Denominator for basic earnings per common share (in shares)	64,901,975	64,729,752	64,874,567	64,722,744
Dilutive effect of employee stock compensation plans (in shares)	35,251	63,382	37,985	65,578
Denominator for diluted earnings per common share (in shares)	64,937,226	64,793,134	64,912,552	64,788,322
Basic earnings per share (per share)	$ 1.75	$ 1.35	$ 3.36	$ 2.70
Diluted earnings per share (per share)	$ 1.75	$ 1.35	$ 3.36	$ 2.69
Excludes employee stock options with exercise prices greater than current market price.	0	0	0	0