Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 182,612	$ 175,731	$ 365,184	$ 343,457
Net interest revenue (expense) from internal sources	0	0	0	0
Net interest revenue	182,612	175,731	365,184	343,457
Provision for credit losses	20,000	4,000	55,000	4,000
Net interest revenue after provision for credit losses	162,612	171,731	310,184	339,457
Other operating revenue	188,882	176,285	348,626	342,302
Other operating expense	254,725	227,113	499,625	447,378
Net direct contribution	96,769	120,903	159,185	234,381
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	96,769	120,903	159,185	234,381
Federal and state income taxes	30,497	40,630	51,925	79,014
Net income	66,272	80,273	107,260	155,367
Net income (loss) attributable to non-controlling interests	471	1,043	(1,105)	1,294
Net income attributable to BOK Financial Corp. shareholders	65,801	79,230	108,365	154,073
Average assets	31,986,042	30,464,072	31,747,257	30,218,751
Average invested capital	3,309,471	3,344,610	3,298,909	3,331,508
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	118,480	108,620	235,116	209,795
Net interest revenue (expense) from internal sources	(14,575)	(12,643)	(29,109)	(25,278)
Net interest revenue	103,905	95,977	206,007	184,517
Provision for credit losses	6,852	(47)	28,423	(8,949)
Net interest revenue after provision for credit losses	97,053	96,024	177,584	193,466
Other operating revenue	51,497	45,273	96,605	87,720
Other operating expense	52,594	50,801	108,663	99,947
Net direct contribution	95,956	90,496	165,526	181,239
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	(598)	(58)	(680)	(14)
Corporate expense allocations	8,883	10,782	17,627	22,023
Net income before taxes	86,475	79,656	147,219	159,202
Federal and state income taxes	33,639	30,986	57,268	61,930
Net income	52,836	48,670	89,951	97,272
Net income (loss) attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	52,836	48,670	89,951	97,272
Average assets	16,973,663	16,262,457	16,971,339	16,266,341
Average invested capital	1,167,840	1,028,989	1,160,485	1,013,117
Operating Segments [Member] | Consumer [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	22,349	21,721	43,799	42,440
Net interest revenue (expense) from internal sources	8,876	6,838	18,229	13,658
Net interest revenue	31,225	28,559	62,028	56,098
Provision for credit losses	1,318	1,614	3,020	3,036
Net interest revenue after provision for credit losses	29,907	26,945	59,008	53,062
Other operating revenue	60,780	59,688	117,139	120,883
Other operating expense	66,146	52,511	124,194	104,817
Net direct contribution	24,541	34,122	51,953	69,128
Gain (loss) on financial instruments, net	15,045	(9,135)	31,626	(5,577)
Change in fair value of mortgage servicing rights	(16,283)	8,010	(44,271)	(512)
Gain (loss) on repossessed assets, net	252	479	406	557
Corporate expense allocations	16,630	18,953	32,608	37,155
Net income before taxes	6,925	14,523	7,106	26,441
Federal and state income taxes	2,694	5,649	2,764	10,286
Net income	4,231	8,874	4,342	16,155
Net income (loss) attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	4,231	8,874	4,342	16,155
Average assets	8,774,881	8,970,936	8,731,085	8,885,400
Average invested capital	266,561	269,388	262,762	270,738
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	6,269	6,221	12,347	11,597
Net interest revenue (expense) from internal sources	7,193	5,487	14,857	11,566
Net interest revenue	13,462	11,708	27,204	23,163
Provision for credit losses	(239)	(399)	(390)	(747)
Net interest revenue after provision for credit losses	13,701	12,107	27,594	23,910
Other operating revenue	75,772	70,599	144,518	137,559
Other operating expense	61,414	58,277	122,098	112,757
Net direct contribution	28,059	24,429	50,014	48,712
Gain (loss) on financial instruments, net	0	(28)	0	(28)
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	10,417	10,187	20,952	20,170
Net income before taxes	17,642	14,214	29,062	28,514
Federal and state income taxes	6,863	5,529	11,305	11,092
Net income	10,779	8,685	17,757	17,422
Net income (loss) attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	10,779	8,685	17,757	17,422
Average assets	5,765,390	5,319,568	5,665,218	5,385,266
Average invested capital	240,693	224,971	236,798	224,247
Corporate, Non-Segment [Member] | Funds Management and Other [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	35,514	39,169	73,922	79,625
Net interest revenue (expense) from internal sources	(1,494)	318	(3,977)	54
Net interest revenue	34,020	39,487	69,945	79,679
Provision for credit losses	12,069	2,832	23,947	10,660
Net interest revenue after provision for credit losses	21,951	36,655	45,998	69,019
Other operating revenue	833	725	(9,636)	(3,860)
Other operating expense	74,571	65,524	144,670	129,857
Net direct contribution	(51,787)	(28,144)	(108,308)	(64,698)
Gain (loss) on financial instruments, net	(15,045)	9,163	(31,626)	5,605
Change in fair value of mortgage servicing rights	16,283	(8,010)	44,271	512
Gain (loss) on repossessed assets, net	346	(421)	274	(543)
Corporate expense allocations	(35,930)	(39,922)	(71,187)	(79,348)
Net income before taxes	(14,273)	12,510	(24,202)	20,224
Federal and state income taxes	(12,699)	(1,534)	(19,412)	(4,294)
Net income	(1,574)	14,044	(4,790)	24,518
Net income (loss) attributable to non-controlling interests	471	1,043	(1,105)	1,294
Net income attributable to BOK Financial Corp. shareholders	(2,045)	13,001	(3,685)	23,224
Average assets	472,108	(88,889)	379,615	(318,256)
Average invested capital	$ 1,634,377	$ 1,821,262	$ 1,638,864	$ 1,823,406