Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator: [Abstract]:
Net income attributable to BOK Financial Corp. shareholders			$ 445,646	$ 334,644	$ 232,668
Less: Earnings allocated to participating securities			3,737	3,561	2,883
Numerator for basic earnings per share - income available to common shareholders			441,909	331,083	229,785
Effect of reallocating undistributed earnings of participating securities			1	2	1
Numerator for diluted earnings per share - income available to common shareholders			$ 441,910	$ 331,085	$ 229,786
Denominator: [Abstract]
Weighted average shares outstanding			67,190,257	65,440,832	65,901,110
Less: Participating securities included in weighted average shares outstanding (in shares)			561,617	695,468	815,483
Denominator for basic earnings per common share (in shares)			66,628,640	64,745,364	65,085,627
Dilutive effect of employee stock compensation plans (in shares)			33,633	60,920	58,271
Denominator for diluted earnings per common share (in shares)			66,662,273	64,806,284	65,143,898
Basic (in dollars per share)	$ 1.50	$ 1.11	$ 6.63	$ 5.11	$ 3.53
Diluted earnings per share (per share)	$ 1.50	$ 1.11	$ 6.63	$ 5.11	$ 3.53
Excludes employee stock options with exercise prices greater than current market price.			0	0	0