Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 187,846	$ 178,636	$ 553,030	$ 522,093
Net interest revenue (expense) from internal sources	0	0	0	0
Net interest revenue	187,846	178,636	553,030	522,093
Provision for credit losses	10,000	7,500	65,000	11,500
Net interest revenue after provision for credit losses	177,846	171,136	488,030	510,593
Other operating revenue	191,342	163,436	539,968	505,738
Other operating expense	262,120	224,628	761,745	672,006
Net direct contribution	107,068	109,944	266,253	344,325
Gain (loss) on financial instruments, net	0	0	0	0
Change in fair value of mortgage servicing rights	0	0	0	0
Gain on repossessed assets, net	0	0	0	0
Corporate expense allocations	0	0	0	0
Net income before taxes	107,068	109,944	266,253	344,325
Federal and state income taxes	31,956	34,128	83,881	113,142
Net income	75,112	75,816	182,372	231,183
Net income (loss) attributable to non-controlling interests	835	925	(270)	2,219
Net income attributable to BOK Financial Corp. shareholders	74,277	74,891	182,642	228,964
Average assets	32,646,473	30,769,733	32,049,183	30,404,430
Average invested capital	3,357,551	3,361,547	3,318,599	3,341,631
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	123,598	109,503	358,714	319,298
Net interest revenue (expense) from internal sources	(15,052)	(13,450)	(44,259)	(38,728)
Net interest revenue	108,546	96,053	314,455	280,570
Provision for credit losses	5,601	997	34,024	(7,952)
Net interest revenue after provision for credit losses	102,945	95,056	280,431	288,522
Other operating revenue	49,642	45,276	146,248	132,996
Other operating expense	53,375	51,960	162,039	151,908
Net direct contribution	99,212	88,372	264,640	269,610
Gain (loss) on financial instruments, net	0	0	0	0
Change in fair value of mortgage servicing rights	0	0	0	0
Gain on repossessed assets, net	1,486	350	806	336
Corporate expense allocations	9,054	10,723	26,681	32,747
Net income before taxes	91,644	77,999	238,765	237,199
Federal and state income taxes	35,650	30,342	92,880	92,270
Net income	55,994	47,657	145,885	144,929
Net income (loss) attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	55,994	47,657	145,885	144,929
Average assets	16,934,587	16,156,446	16,958,999	16,229,307
Average invested capital	1,170,465	1,062,053	1,161,996	1,028,013
Operating Segments [Member] | Consumer [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	22,098	21,551	65,897	63,993
Net interest revenue (expense) from internal sources	9,263	7,216	27,492	20,874
Net interest revenue	31,361	28,767	93,389	84,867
Provision for credit losses	1,157	1,431	4,177	4,467
Net interest revenue after provision for credit losses	30,204	27,336	89,212	80,400
Other operating revenue	64,635	57,349	181,774	178,232
Other operating expense	64,995	51,027	189,188	155,844
Net direct contribution	29,844	33,658	81,798	102,788
Gain (loss) on financial instruments, net	(1,087)	7,386	30,539	1,809
Change in fair value of mortgage servicing rights	2,327	(11,758)	(41,944)	(12,269)
Gain on repossessed assets, net	161	331	566	888
Corporate expense allocations	16,905	18,921	49,513	56,075
Net income before taxes	14,340	10,696	21,446	37,141
Federal and state income taxes	5,578	4,161	8,342	14,448
Net income	8,762	6,535	13,104	22,693
Net income (loss) attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	8,762	6,535	13,104	22,693
Average assets	8,827,816	8,843,926	8,763,564	8,871,423
Average invested capital	275,358	264,540	267,123	268,427
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	9,274	6,674	21,622	18,271
Net interest revenue (expense) from internal sources	7,401	5,834	22,258	17,400
Net interest revenue	16,675	12,508	43,880	35,671
Provision for credit losses	(89)	(190)	(479)	(937)
Net interest revenue after provision for credit losses	16,764	12,698	44,359	36,608
Other operating revenue	73,523	66,541	218,042	204,100
Other operating expense	64,426	57,356	186,524	170,113
Net direct contribution	25,861	21,883	75,877	70,595
Gain (loss) on financial instruments, net	(42)	(176)	(42)	(204)
Change in fair value of mortgage servicing rights	0	0	0	0
Gain on repossessed assets, net	0	0	0	0
Corporate expense allocations	10,912	9,841	31,864	30,011
Net income before taxes	14,907	11,866	43,971	40,380
Federal and state income taxes	5,799	4,616	17,105	15,708
Net income	9,108	7,250	26,866	24,672
Net income (loss) attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	9,108	7,250	26,866	24,672
Average assets	6,413,735	5,433,238	5,916,545	5,401,433
Average invested capital	244,291	226,477	238,917	225,222
Corporate, Non-Segment [Member] | Funds Management and Other [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	32,876	40,908	106,797	120,531
Net interest revenue (expense) from internal sources	(1,612)	400	(5,491)	454
Net interest revenue	31,264	41,308	101,306	120,985
Provision for credit losses	3,331	5,262	27,278	15,922
Net interest revenue after provision for credit losses	27,933	36,046	74,028	105,063
Other operating revenue	3,542	(5,730)	(6,096)	(9,590)
Other operating expense	79,324	64,285	223,994	194,141
Net direct contribution	(47,849)	(33,969)	(156,062)	(98,668)
Gain (loss) on financial instruments, net	1,129	(7,210)	(30,497)	(1,605)
Change in fair value of mortgage servicing rights	(2,327)	11,758	41,944	12,269
Gain on repossessed assets, net	(1,647)	(681)	(1,372)	(1,224)
Corporate expense allocations	(36,871)	(39,485)	(108,058)	(118,833)
Net income before taxes	(13,823)	9,383	(37,929)	29,605
Federal and state income taxes	(15,071)	(4,991)	(34,446)	(9,284)
Net income	1,248	14,374	(3,483)	38,889
Net income (loss) attributable to non-controlling interests	835	925	(270)	2,219
Net income attributable to BOK Financial Corp. shareholders	413	13,449	(3,213)	36,670
Average assets	470,335	336,123	410,075	(97,733)
Average invested capital	$ 1,667,437	$ 1,808,477	$ 1,650,563	$ 1,819,969