Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 178,636	$ 166,791	$ 522,093	$ 495,530
Net interest revenue (expense) from internal sources	0	0	0	0
Net interest revenue	178,636	166,791	522,093	495,530
Provision for credit losses	7,500	0	11,500	0
Net interest revenue after provision for credit losses	171,136	166,791	510,593	495,530
Other operating revenue	163,436	164,971	505,738	470,055
Other operating expense	224,628	221,834	672,006	621,645
Net direct contribution	109,944	109,928	344,325	343,940
Corporate expense allocations	0	0	0	0
Net income before taxes	109,944	109,928	344,325	343,940
Federal and state income taxes	34,128	33,802	113,142	114,042
Net income	75,816	76,126	231,183	229,898
Net income attributable to non-controlling interests	925	494	2,219	1,781
Net income attributable to BOK Financial Corp. shareholders	74,891	75,632	228,964	228,117
Average assets	30,769,733	28,115,557	30,404,430	27,616,927
Average invested capital	$ 3,361,547	$ 3,213,103	$ 3,341,631	$ 3,142,374
Performance measurements: [Abstract]
Return on average assets	0.97%	1.07%	1.01%	1.10%
Return on average invested capital	8.84%	9.34%	9.16%	9.71%
Efficiency ratio	64.34%	67.18%	64.48%	63.58%
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 109,495	$ 95,423	$ 319,279	$ 281,064
Net interest revenue (expense) from internal sources	(12,730)	(9,796)	(37,928)	(33,419)
Net interest revenue	96,765	85,627	281,351	247,645
Provision for credit losses	828	(1,702)	(8,122)	(8,894)
Net interest revenue after provision for credit losses	95,937	87,329	289,473	256,539
Other operating revenue	44,899	45,121	133,363	126,527
Other operating expense	52,499	55,532	155,855	155,529
Net direct contribution	88,337	76,918	266,981	227,537
Corporate expense allocations	14,668	13,081	43,970	42,024
Net income before taxes	73,669	63,837	223,011	185,513
Federal and state income taxes	28,657	24,833	86,751	72,165
Net income	45,012	39,004	136,260	113,348
Net income attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	45,012	39,004	136,260	113,348
Average assets	13,544,828	11,508,661	13,114,958	11,222,847
Average invested capital	$ 1,062,053	$ 940,091	$ 1,028,013	$ 937,281
Performance measurements: [Abstract]
Return on average assets	1.32%	1.35%	1.39%	1.35%
Return on average invested capital	16.83%	16.47%	17.74%	16.21%
Efficiency ratio	36.90%	42.45%	37.51%	41.39%
Operating Segments [Member] | Consumer [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 21,578	$ 19,742	$ 64,030	$ 61,672
Net interest revenue (expense) from internal sources	7,688	9,517	23,226	28,354
Net interest revenue	29,266	29,259	87,256	90,026
Provision for credit losses	1,488	1,599	1,488	1,599
Net interest revenue after provision for credit losses	27,778	27,660	85,768	88,427
Other operating revenue	52,978	55,243	167,773	154,030
Other operating expense	50,608	49,105	158,404	141,462
Net direct contribution	30,148	33,798	95,137	100,995
Corporate expense allocations	21,845	18,229	64,779	57,768
Net income before taxes	8,303	15,569	30,358	43,227
Federal and state income taxes	3,230	6,056	11,809	16,815
Net income	5,073	9,513	18,549	26,412
Net income attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	5,073	9,513	18,549	26,412
Average assets	7,286,709	7,123,786	7,307,097	7,091,118
Average invested capital	$ 264,540	$ 271,705	$ 268,427	$ 278,396
Performance measurements: [Abstract]
Return on average assets	0.28%	0.53%	0.34%	0.50%
Return on average invested capital	7.61%	13.89%	9.24%	12.68%
Efficiency ratio	56.97%	58.99%	58.28%	56.26%
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 6,680	$ 5,956	$ 18,289	$ 17,574
Net interest revenue (expense) from internal sources	5,161	5,191	15,712	14,594
Net interest revenue	11,841	11,147	34,001	32,168
Provision for credit losses	2	(125)	(745)	323
Net interest revenue after provision for credit losses	11,839	11,272	34,746	31,845
Other operating revenue	63,095	61,001	191,316	180,790
Other operating expense	57,742	56,301	171,760	160,846
Net direct contribution	17,192	15,972	54,302	51,789
Corporate expense allocations	10,858	12,276	33,154	36,130
Net income before taxes	6,334	3,696	21,148	15,659
Federal and state income taxes	2,464	1,438	8,227	6,091
Net income	3,870	2,258	12,921	9,568
Net income attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	3,870	2,258	12,921	9,568
Average assets	4,629,506	4,324,204	4,696,750	4,499,858
Average invested capital	$ 226,477	$ 220,489	$ 225,222	$ 212,729
Performance measurements: [Abstract]
Return on average assets	0.38%	0.26%	0.42%	0.33%
Return on average invested capital	7.75%	5.06%	8.66%	6.89%
Efficiency ratio	76.56%	77.69%	75.69%	75.13%
Corporate, Non-Segment [Member] | Funds Management and Other [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 40,883	$ 45,670	$ 120,495	$ 135,220
Net interest revenue (expense) from internal sources	(119)	(4,912)	(1,010)	(9,529)
Net interest revenue	40,764	40,758	119,485	125,691
Provision for credit losses	5,182	228	18,879	6,972
Net interest revenue after provision for credit losses	35,582	40,530	100,606	118,719
Other operating revenue	2,464	3,606	13,286	8,708
Other operating expense	63,779	60,896	185,987	163,808
Net direct contribution	(25,733)	(16,760)	(72,095)	(36,381)
Corporate expense allocations	(47,371)	(43,586)	(141,903)	(135,922)
Net income before taxes	21,638	26,826	69,808	99,541
Federal and state income taxes	(223)	1,475	6,355	18,971
Net income	21,861	25,351	63,453	80,570
Net income attributable to non-controlling interests	925	494	2,219	1,781
Net income attributable to BOK Financial Corp. shareholders	20,936	24,857	61,234	78,789
Average assets	5,308,690	5,158,906	5,285,625	4,803,104
Average invested capital	$ 1,808,477	$ 1,780,818	$ 1,819,969	$ 1,713,968