Consolidated Statements of Earnings (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Interest revenue [Abstract]
Loans	$ 188,091	$ 160,895
Residential mortgage loans held for sale	1,844	1,836
Trading securities	7,738	5,183
Investment securities	3,857	4,171
Available for sale securities	45,959	43,372
Fair value option securities	4,819	2,380
Restricted equity securities	5,117	4,309
Interest-bearing cash and cash equivalents	7,982	4,244
Total interest revenue	265,407	226,390
Interest expense [Abstract]
Deposits	18,219	11,354
Borrowed funds	25,449	11,829
Subordinated debentures	2,003	2,025
Total interest expense	45,671	25,208
Net interest revenue	219,736	201,182
Provision for credit losses	(5,000)	0
Net interest revenue after provision for credit losses	224,736	201,182
Other operating revenue [Abstract]
Brokerage and trading revenue	30,648	33,623
Transaction card revenue	20,990	27,380
Fiduciary and asset management revenue	41,832	38,631
Deposit service charges and fees	27,161	27,777
Mortgage banking revenue	26,025	25,191
Other revenue	12,330	11,752
Total fees and commissions	158,986	164,354
Other gains (losses), net	(664)	3,627
Loss on derivatives, net	(5,685)	(450)
Loss on fair value option securities, net	(17,564)	(1,140)
Change in fair value of mortgage servicing rights	21,206	1,856
Gain (loss) on available for sale securities, net	(290)	2,049
Total other operating revenue	155,989	170,296
Other operating expense [Abstract]
Personnel	139,947	136,425
Business promotion	6,010	6,717
Professional fees and services	10,200	11,417
Net occupancy and equipment	24,046	21,624
Insurance	6,593	6,404
Data processing and communications	27,817	34,902
Printing, postage and supplies	4,089	3,851
Net losses and operating expenses of repossessed assets	7,705	1,009
Amortization of intangible assets	1,300	1,802
Mortgage banking costs	10,149	13,003
Other expense	6,574	7,557
Total other operating expense	244,430	244,711
Net income before taxes	136,295	126,767
Federal and state income taxes	30,948	38,103
Net income	105,347	88,664
Net income (loss) attributable to non-controlling interests	(215)	308
Net income attributable to BOK Financial Corporation shareholders	$ 105,562	$ 88,356
Earnings per share: [Abstract]
Basic	$ 1.61	$ 1.35
Diluted	$ 1.61	$ 1.35
Average shares used in computation: [Abstract]
Basic	64,847,334	64,715,964
Diluted	64,888,033	64,783,737
Dividends declared per share	$ 0.45	$ 0.44