Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator: [Abstract]
Net income attributable to BOK Financial Corp. shareholders	$ 142,231	$ 117,256	$ 390,406	$ 337,190
Less: Earnings allocated to participating securities	875	963	2,553	2,940
Numerator for basic earnings per share – income available to common shareholders	141,356	116,293	387,853	334,250
Effect of reallocating undistributed earnings of participating securities	1	1	1	1
Numerator for diluted earnings per share – income available to common shareholders	$ 141,357	$ 116,294	$ 387,854	$ 334,251
Denominator: [Abstract]
Weighted average shares outstanding (in shares)	71,033,405	65,438,849	71,425,855	65,455,306
Less: Participating securities included in weighted average shares (in shares)	437,098	537,754	472,311	571,987
Denominator for basic earnings per common share (in shares)	70,596,307	64,901,095	70,953,544	64,883,319
Dilutive effect of employee stock compensation plans (in shares)	13,617	33,256	15,301	36,409
Denominator for diluted earnings per common share (in shares)	70,609,924	64,934,351	70,968,845	64,919,728
Basic earnings per share (per share)	$ 2.00	$ 1.79	$ 5.47	$ 5.15
Diluted earnings per share (per share)	$ 2.00	$ 1.79	$ 5.47	$ 5.15
Excludes employee stock options with exercise prices greater than current market price.	0	0	0	0