Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator: [Abstract]
Net income attributable to BOK Financial Corp. shareholders	$ 105,562	$ 88,356
Less: Earnings allocated to participating securities	1,022	1,003
Numerator for basic earnings per share – income available to common shareholders	104,540	87,353
Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted	0	0
Numerator for diluted earnings per share – income available to common shareholders	$ 104,540	$ 87,353
Denominator: [Abstract]
Weighted average shares outstanding (in shares)	65,479,482	65,457,772
Less: Participating securities included in weighted average shares (in shares)	632,148	741,808
Denominator for basic earnings per common share (in shares)	64,847,334	64,715,964
Dilutive effect of employee stock compensation plans (in shares)	40,699	67,773
Denominator for diluted earnings per common share (in shares)	64,888,033	64,783,737
Basic earnings per share (per share)	$ 1.61	$ 1.35
Diluted earnings per share (per share)	$ 1.61	$ 1.35
Excludes employee stock options with exercise prices greater than current market price.	0	0