Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 280,227	$ 271,750	$ 840,956	$ 811,214
Net interest revenue (expense) from internal sources	0	0	0	0
Net interest revenue	280,227	271,750	840,956	811,214
Provision for credit losses	(23,000)	0	(83,000)	229,092
Net interest revenue after provision for credit losses	303,227	271,750	923,956	582,122
Other operating revenue	229,832	229,938	598,332	643,532
Other operating expense	291,277	297,044	878,213	861,637
Net direct contribution	241,782	204,644	644,075	364,017
Gain (loss) on financial instruments, net	0	0	0	0
Change in fair value of mortgage servicing rights	0	0	0	0
Gain (loss) on repossessed assets, net	0	0	0	0
Corporate expense allocations	0	0	0	0
Net income before taxes	241,782	204,644	644,075	364,017
Federal and state income taxes	54,061	50,552	144,939	83,655
Net income	187,721	154,092	499,136	280,362
Net income (loss) attributable to non-controlling interests	(601)	58	(1,667)	(444)
Net income attributable to BOK Financial Corp. shareholders	188,322	154,034	500,803	280,806
Average assets	49,499,149	48,931,755	49,999,262	48,139,370
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	150,211	173,248	457,953	549,464
Net interest revenue (expense) from internal sources	(16,107)	(23,302)	(62,941)	(103,002)
Net interest revenue	134,104	149,946	395,012	446,462
Provision for credit losses	2,807	22,599	33,061	53,241
Net interest revenue after provision for credit losses	131,297	127,347	361,951	393,221
Other operating revenue	92,511	52,021	204,358	138,139
Other operating expense	68,301	66,846	206,630	190,531
Net direct contribution	155,507	112,522	359,679	340,829
Gain (loss) on financial instruments, net	44	38	111	135
Change in fair value of mortgage servicing rights	0	0	0	0
Gain (loss) on repossessed assets, net	(3,945)	(4,332)	12,355	(4,132)
Corporate expense allocations	11,769	5,172	37,015	19,514
Net income before taxes	139,837	103,056	335,130	317,318
Federal and state income taxes	37,143	27,959	90,130	86,254
Net income	102,694	75,097	245,000	231,064
Net income (loss) attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	102,694	75,097	245,000	231,064
Average assets	28,474,182	28,000,183	28,228,840	26,759,150
Operating Segments [Member] | Consumer [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	16,967	15,821	51,205	60,492
Net interest revenue (expense) from internal sources	10,255	17,309	21,936	55,840
Net interest revenue	27,222	33,130	73,141	116,332
Provision for credit losses	928	79	2,489	1,870
Net interest revenue after provision for credit losses	26,294	33,051	70,652	114,462
Other operating revenue	44,401	67,808	134,396	190,062
Other operating expense	49,483	59,155	157,558	171,172
Net direct contribution	21,212	41,704	47,490	133,352
Gain (loss) on financial instruments, net	(5,949)	1,540	(18,427)	95,660
Change in fair value of mortgage servicing rights	12,945	3,441	33,778	(85,800)
Gain (loss) on repossessed assets, net	0	41	41	81
Corporate expense allocations	11,516	10,691	34,590	31,749
Net income before taxes	16,692	36,035	28,292	111,544
Federal and state income taxes	4,260	9,180	7,214	28,411
Net income	12,432	26,855	21,078	83,133
Net income (loss) attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	12,432	26,855	21,078	83,133
Average assets	10,083,593	9,898,112	9,976,742	9,889,687
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	55,697	34,098	157,217	82,823
Net interest revenue (expense) from internal sources	(501)	(11,113)	(1,375)	(14,054)
Net interest revenue	55,196	22,985	155,842	68,769
Provision for credit losses	(70)	(51)	(153)	(188)
Net interest revenue after provision for credit losses	55,266	23,036	155,995	68,957
Other operating revenue	97,888	111,152	243,160	315,707
Other operating expense	87,417	82,868	245,411	241,627
Net direct contribution	65,737	51,320	153,744	143,037
Gain (loss) on financial instruments, net	0	0	0	7
Change in fair value of mortgage servicing rights	0	0	0	0
Gain (loss) on repossessed assets, net	0	0	0	0
Corporate expense allocations	10,101	9,397	30,330	25,866
Net income before taxes	55,636	41,923	123,414	117,178
Federal and state income taxes	14,230	10,711	31,565	29,999
Net income	41,406	31,212	91,849	87,179
Net income (loss) attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	41,406	31,212	91,849	87,179
Average assets	19,109,700	16,204,510	18,987,234	14,887,947
Funds Management and Other [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	57,352	48,583	174,581	118,435
Net interest revenue (expense) from internal sources	6,353	17,106	42,380	61,216
Net interest revenue	63,705	65,689	216,961	179,651
Provision for credit losses	(26,665)	(22,627)	(118,397)	174,169
Net interest revenue after provision for credit losses	90,370	88,316	335,358	5,482
Other operating revenue	(4,968)	(1,043)	16,418	(376)
Other operating expense	86,076	88,175	268,614	258,307
Net direct contribution	(674)	(902)	83,162	(253,201)
Gain (loss) on financial instruments, net	5,905	(1,578)	18,316	(95,802)
Change in fair value of mortgage servicing rights	(12,945)	(3,441)	(33,778)	85,800
Gain (loss) on repossessed assets, net	3,945	4,291	(12,396)	4,051
Corporate expense allocations	(33,386)	(25,260)	(101,935)	(77,129)
Net income before taxes	29,617	23,630	157,239	(182,023)
Federal and state income taxes	(1,572)	2,702	16,030	(61,009)
Net income	31,189	20,928	141,209	(121,014)
Net income (loss) attributable to non-controlling interests	(601)	58	(1,667)	(444)
Net income attributable to BOK Financial Corp. shareholders	31,790	20,870	142,876	(120,570)
Average assets	$ (8,168,326)	$ (5,171,050)	$ (7,193,554)	$ (3,397,414)