Consolidated Statements of Earnings - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest and dividend revenue [Abstract]
Loans	$ 1,123,791	$ 891,587	$ 696,479
Residential mortgage loans held for sale	7,105	8,123	8,706
Trading securities	61,595	57,531	17,002
Investment securities	13,426	14,775	16,121
Available for sale securities	254,031	197,317	177,070
Fair value option securities	32,936	15,205	16,755
Restricted equity securities	26,860	21,555	18,490
Interest-bearing cash and cash equivalents	12,214	22,333	22,128
Total interest revenue	1,531,958	1,228,426	972,751
Interest Expense [Abstract]
Deposits	175,538	95,517	53,803
Borrowed funds	228,428	138,215	69,008
Subordinated debentures	15,113	9,827	8,239
Total interest expense	419,079	243,559	131,050
Net interest and dividend revenue	1,112,879	984,867	841,701
Provision for credit losses	44,000	8,000	(7,000)
Net interest and dividend revenue after provision for credit losses	1,068,879	976,867	848,701
Total fees and commissions	702,201	643,176	681,014
Other gains (losses), net	9,351	(2,265)	11,434
Gain (loss) on derivatives, net	14,951	(422)	779
Gain (loss) on fair value option securities, net	15,787	(25,572)	(2,733)
Change in fair value of mortgage servicing rights	(53,517)	4,668	172
Gain (loss) on available for sale securities, net	5,597	(2,801)	4,428
Total other operating revenue	694,370	616,784	695,094
Other operating expense [Abstract]
Personnel	660,565	583,131	573,408
Business promotion	35,662	30,523	28,877
Charitable contributions to BOKF Foundation	3,000	2,846	2,000
Professional fees and services	54,861	59,099	51,067
Net occupancy and equipment	110,275	97,981	86,477
Insurance	20,906	23,318	19,653
Data processing and communications	124,983	114,796	146,970
Printing, postage and supplies	16,517	17,169	15,689
Net losses and operating expenses of repossessed assets	6,707	17,052	9,687
Amortization of intangible assets	20,618	9,620	6,779
Mortgage banking costs	50,685	46,298	52,856
Other expense	27,602	26,333	32,054
Total other operating expense	1,132,381	1,028,166	1,025,517
Net income before taxes	630,868	565,485	518,278
Federal and state income taxes	130,183	119,061	182,593
Net income	500,685	446,424	335,685
Net income (loss) attributable to Non-controlling interests	(73)	778	1,041
Net income attributable to BOK Financial Corporation shareholders	$ 500,758	$ 445,646	$ 334,644
Earnings per share: [Abstract]
Basic (in dollars per share)	$ 7.03	$ 6.63	$ 5.11
Diluted (in dollars per share)	$ 7.03	$ 6.63	$ 5.11
Average shares used in computation: [Abstract]
Basic (in shares)	70,787,700	66,628,640	64,745,364
Diluted (in shares)	70,802,612	66,662,273	64,806,284
Dividends declared per share (in dollars per share)	$ 2.01	$ 1.90	$ 1.77
Brokerage and trading revenue [Member]
Total fees and commissions	$ 159,826	$ 108,323	$ 131,601
Transaction card revenue [Member]
Total fees and commissions	87,216	84,025	119,988
Fiduciary and asset management revenue [Member]
Total fees and commissions	177,025	184,703	162,889
Deposit service charges and fees [Member]
Total fees and commissions	112,485	112,153	112,079
Mortgage banking revenue [Member]
Total fees and commissions	107,541	97,787	104,719
Other revenue [Member]
Total fees and commissions	$ 58,108	$ 56,185	$ 49,738