Consolidated Statements of Earnings (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Interest revenue [Abstract]
Loans	$ 279,872	$ 188,091
Residential mortgage loans held for sale	1,663	1,844
Trading securities	18,695	7,738
Investment securities	4,034	3,857
Available for sale securities	56,831	45,959
Fair value option securities	5,237	4,819
Restricted equity securities	6,345	5,117
Interest-bearing cash and cash equivalents	3,397	7,982
Total interest revenue	376,074	265,407
Interest expense [Abstract]
Deposits	37,417	18,219
Borrowed funds	56,810	25,449
Subordinated debentures	3,745	2,003
Total interest expense	97,972	45,671
Net interest revenue	278,102	219,736
Provision for credit losses	8,000	(5,000)
Net interest revenue after provision for credit losses	270,102	224,736
Total fees and commissions	160,552	159,614
Other gains (losses), net	2,976	(1,292)
Gain (loss) on derivatives, net	4,667	(5,685)
Gain (loss) on fair value option securities, net	9,665	(17,564)
Change in fair value of mortgage servicing rights	(20,666)	21,206
Gain (loss) on available for sale securities, net	76	(290)
Total other operating revenue	157,270	155,989
Other operating expense [Abstract]
Personnel	169,228	139,947
Business promotion	7,874	6,010
Professional fees and services	16,139	10,200
Net occupancy and equipment	29,521	24,046
Insurance	4,839	6,593
Data processing and communications	31,449	27,817
Printing, postage and supplies	4,885	4,089
Net losses and operating expenses of repossessed assets	1,996	7,705
Amortization of intangible assets	5,191	1,300
Mortgage banking costs	9,906	10,149
Other expense	6,129	6,574
Total other operating expense	287,157	244,430
Net income before taxes	140,215	136,295
Federal and state income taxes	29,950	30,948
Net income	110,265	105,347
Net income attributable to non-controlling interests	(347)	(215)
Net income attributable to BOK Financial Corporation shareholders	$ 110,612	$ 105,562
Earnings per share: [Abstract]
Basic	$ 1.54	$ 1.61
Diluted	$ 1.54	$ 1.61
Average shares used in computation: [Abstract]
Basic	71,387,070	64,847,334
Diluted	71,404,388	64,888,033
Dividends declared per share	$ 0.50	$ 0.45
Brokerage and trading revenue [Member]
Total fees and commissions	$ 31,617	$ 30,648
Transaction card revenue [Member]
Total fees and commissions	20,738	20,990
Fiduciary and asset management revenue [Member]
Total fees and commissions	43,358	41,832
Deposit service charges and fees [Member]
Total fees and commissions	28,243	27,161
Mortgage banking revenue [Member]
Total fees and commissions	23,834	26,025
Other revenue [Member]
Total fees and commissions	$ 12,762	$ 12,958