Consolidated Statements of Earnings (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Interest revenue [Abstract]
Loans	$ 243,218	$ 279,872
Residential mortgage loans held for sale	1,123	1,663
Trading securities	11,760	18,695
Investment securities	3,121	4,034
Available for sale securities	69,720	56,831
Fair value option securities	11,708	5,237
Restricted equity securities	5,894	6,345
Interest-bearing cash and cash equivalents	2,393	3,397
Total interest revenue	348,937	376,074
Interest expense [Abstract]
Deposits	46,159	37,417
Borrowed funds	37,785	56,810
Subordinated debentures	3,633	3,745
Total interest expense	87,577	97,972
Net interest revenue	261,360	278,102
Provision for credit losses	93,771	8,000
Net interest revenue after provision for credit losses	167,589	270,102
Total fees and commissions	192,724	160,552
Other gains (losses), net	(10,741)	2,976
Gain on derivatives, net	18,420	4,667
Gain on fair value option securities, net	68,393	9,665
Change in fair value of mortgage servicing rights	(88,480)	(20,666)
Gain on available for sale securities, net	3	76
Total other operating revenue	180,319	157,270
Other operating expense [Abstract]
Personnel	156,181	169,228
Business promotion	6,215	7,874
Professional fees and services	12,948	16,139
Net occupancy and equipment	26,061	29,521
Insurance	4,980	4,839
Data processing and communications	32,743	31,449
Printing, postage and supplies	4,272	4,885
Net losses and operating expenses of repossessed assets	1,531	1,996
Amortization of intangible assets	5,094	5,191
Mortgage banking costs	10,545	9,906
Other expense	8,054	6,129
Total other operating expense	268,624	287,157
Net income before taxes	79,284	140,215
Federal and state income taxes	17,300	29,950
Net income	61,984	110,265
Net income (loss) attributable to non-controlling interests	(95)	(347)
Net income attributable to BOK Financial Corporation shareholders	$ 62,079	$ 110,612
Earnings per share: [Abstract]
Basic	$ 0.88	$ 1.54
Diluted	$ 0.88	$ 1.54
Average shares used in computation: [Abstract]
Basic	70,123,685	71,387,070
Diluted	70,130,166	71,404,388
Dividends declared per share	$ 0.51	$ 0.50
Brokerage and trading revenue [Member]
Total fees and commissions	$ 50,779	$ 31,617
Transaction card revenue [Member]
Total fees and commissions	21,881	20,738
Fiduciary and asset management revenue [Member]
Total fees and commissions	44,458	43,358
Deposit service charges and fees [Member]
Total fees and commissions	26,130	28,243
Mortgage banking revenue [Member]
Total fees and commissions	37,167	23,834
Other revenue [Member]
Total fees and commissions	$ 12,309	$ 12,762