Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 280,420	$ 261,360
Net interest revenue (expense) from internal sources	0	0
Net interest revenue	280,420	261,360
Provision for credit losses	(25,000)	93,771
Net interest revenue after provision for credit losses	305,420	167,589
Other operating revenue	163,897	180,319
Other operating expense	282,627	268,624
Net direct contribution	186,690	79,284
Gain (loss) on financial instruments, net	0	0
Change in fair value of mortgage servicing rights	0	0
Gain (loss) on repossessed assets, net	0	0
Corporate expense allocations	0	0
Net income before taxes	186,690	79,284
Federal and state income taxes	42,382	17,300
Net income	144,308	61,984
Net income (loss) attributable to non-controlling interests	(1,752)	(95)
Net income attributable to BOK Financial Corp. shareholders	146,060	62,079
Average assets	50,310,633	45,720,618
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	155,799	201,902
Net interest revenue (expense) from internal sources	(25,794)	(50,495)
Net interest revenue	130,005	151,407
Provision for credit losses	13,985	16,880
Net interest revenue after provision for credit losses	116,020	134,527
Other operating revenue	46,579	38,220
Other operating expense	66,979	60,752
Net direct contribution	95,620	111,995
Gain (loss) on financial instruments, net	33	49
Change in fair value of mortgage servicing rights	0	0
Gain (loss) on repossessed assets, net	12,737	9
Corporate expense allocations	12,734	8,905
Net income before taxes	95,656	103,148
Federal and state income taxes	25,983	28,173
Net income	69,673	74,975
Net income (loss) attributable to non-controlling interests	0	0
Net income attributable to BOK Financial Corp. shareholders	69,673	74,975
Average assets	28,047,052	24,687,976
Operating Segments [Member] | Consumer [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	16,686	25,876
Net interest revenue (expense) from internal sources	4,288	18,056
Net interest revenue	20,974	43,932
Provision for credit losses	1,136	1,256
Net interest revenue after provision for credit losses	19,838	42,676
Other operating revenue	52,282	55,062
Other operating expense	55,743	53,844
Net direct contribution	16,377	43,894
Gain (loss) on financial instruments, net	(29,616)	86,764
Change in fair value of mortgage servicing rights	33,874	(88,480)
Gain (loss) on repossessed assets, net	41	13
Corporate expense allocations	11,487	10,389
Net income before taxes	9,189	31,802
Federal and state income taxes	2,340	8,101
Net income	6,849	23,701
Net income (loss) attributable to non-controlling interests	0	0
Net income attributable to BOK Financial Corp. shareholders	6,849	23,701
Average assets	9,755,539	9,850,853
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	48,554	14,366
Net interest revenue (expense) from internal sources	(200)	4,538
Net interest revenue	48,354	18,904
Provision for credit losses	(29)	(48)
Net interest revenue after provision for credit losses	48,383	18,952
Other operating revenue	66,123	97,881
Other operating expense	78,565	78,192
Net direct contribution	35,941	38,641
Gain (loss) on financial instruments, net	0	7
Change in fair value of mortgage servicing rights	0	0
Gain (loss) on repossessed assets, net	0	0
Corporate expense allocations	9,887	8,265
Net income before taxes	26,054	30,383
Federal and state income taxes	6,672	7,810
Net income	19,382	22,573
Net income (loss) attributable to non-controlling interests	0	0
Net income attributable to BOK Financial Corp. shareholders	19,382	22,573
Average assets	18,645,865	12,723,412
Funds Management and Other [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	59,381	19,216
Net interest revenue (expense) from internal sources	21,706	27,901
Net interest revenue	81,087	47,117
Provision for credit losses	(40,092)	75,683
Net interest revenue after provision for credit losses	121,179	(28,566)
Other operating revenue	(1,087)	(10,844)
Other operating expense	81,340	75,836
Net direct contribution	38,752	(115,246)
Gain (loss) on financial instruments, net	29,583	(86,820)
Change in fair value of mortgage servicing rights	(33,874)	88,480
Gain (loss) on repossessed assets, net	(12,778)	(22)
Corporate expense allocations	(34,108)	(27,559)
Net income before taxes	55,791	(86,049)
Federal and state income taxes	7,387	(26,784)
Net income	48,404	(59,265)
Net income (loss) attributable to non-controlling interests	(1,752)	(95)
Net income attributable to BOK Financial Corp. shareholders	50,156	(59,170)
Average assets	$ (6,137,823)	$ (1,541,623)