Reportable Segments (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 665,194bokf_NirExpenseFromExternalSources	$ 674,477bokf_NirExpenseFromExternalSources	$ 707,549bokf_NirExpenseFromExternalSources
Net interest revenue (expense) from internal sources	0bokf_NirExpenseFromInternalSources	0bokf_NirExpenseFromInternalSources	0bokf_NirExpenseFromInternalSources
Net interest revenue	665,194us-gaap_InterestIncomeExpenseNet	674,477us-gaap_InterestIncomeExpenseNet	707,549us-gaap_InterestIncomeExpenseNet
Provision for credit losses	0	(27,900)	(22,000)
Net interest revenue after provision for credit losses	665,194	702,377	729,549
Other operating revenue	612,659us-gaap_NoninterestIncome	614,472us-gaap_NoninterestIncome	653,678us-gaap_NoninterestIncome
Operating expense	847,522us-gaap_NoninterestExpense	840,620us-gaap_NoninterestExpense	840,363us-gaap_NoninterestExpense
Net direct contribution	430,331bokf_Netdirectcontribution	476,229bokf_Netdirectcontribution	542,864bokf_Netdirectcontribution
Corporate expense allocations	0bokf_CorporateExpenseAllocations	0bokf_CorporateExpenseAllocations	0bokf_CorporateExpenseAllocations
Net income before taxes	430,331	476,229	542,864
Federal and state income taxes	134,852us-gaap_IncomeTaxExpenseBenefit	157,298us-gaap_IncomeTaxExpenseBenefit	188,740us-gaap_IncomeTaxExpenseBenefit
Net income	295,479us-gaap_ProfitLoss	318,931us-gaap_ProfitLoss	354,124us-gaap_ProfitLoss
Net income attributable to non-controlling interests	3,044	2,322	2,933
Net income attributable to BOK Financial Corp. shareholders	292,435us-gaap_NetIncomeLoss	316,609us-gaap_NetIncomeLoss	351,191us-gaap_NetIncomeLoss
Average assets	27,998,858bokf_AverageAssetsForReportingPeriod	27,381,094bokf_AverageAssetsForReportingPeriod	26,289,150bokf_AverageAssetsForReportingPeriod
Average invested capital	3,210,761	3,011,082	2,905,955
Performance measurements: [Abstract]
Return on average assets	1.04%	1.16%	1.34%
Return on average invested capital	9.11%	10.51%	12.09%
Efficiency ratio	64.50%bokf_SegmentReportingEfficiencyRatio	64.60%bokf_SegmentReportingEfficiencyRatio	62.03%bokf_SegmentReportingEfficiencyRatio
Operating Segments [Member] \| Commercial [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	381,687	363,961	366,243
Net interest revenue (expense) from internal sources	(43,934)	(51,587)	(58,835)
Net interest revenue	337,753	312,374	307,408
Provision for credit losses	(7,447)	(4,372)	9,463
Net interest revenue after provision for credit losses	345,200	316,746	297,945
Other operating revenue	169,704	163,206	162,085
Operating expense	201,748	190,306	192,396
Net direct contribution	313,156	289,646	267,634
Corporate expense allocations	41,338	44,865	44,330
Net income before taxes	271,818	244,781	223,304
Federal and state income taxes	105,737	95,220	86,865
Net income	166,081	149,561	136,439
Net income attributable to non-controlling interests	0	0	0
Net income attributable to BOK Financial Corp. shareholders	166,081	149,561	136,439
Average assets	11,384,508	10,386,235	9,844,145
Average invested capital	946,383	906,717	882,036
Performance measurements: [Abstract]
Return on average assets	1.46%	1.44%	1.39%
Return on average invested capital	17.58%	16.49%	15.47%
Efficiency ratio	39.57%	40.24%	42.26%
Operating Segments [Member] \| Consumer [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	95,910	100,153	102,321
Net interest revenue (expense) from internal sources	32,170	34,850	36,700
Net interest revenue	128,080	135,003	139,021
Provision for credit losses	5,405	5,532	10,588
Net interest revenue after provision for credit losses	122,675	129,471	128,433
Other operating revenue	200,815	225,336	271,723
Operating expense	196,082	189,099	206,598
Net direct contribution	127,408	165,708	193,558
Corporate expense allocations	67,040	60,005	64,239
Net income before taxes	60,368	105,703	129,319
Federal and state income taxes	23,483	41,118	50,305
Net income	36,885	64,585	79,014
Net income attributable to non-controlling interests	0	0	0
Net income attributable to BOK Financial Corp. shareholders	36,885	64,585	79,014
Average assets	6,555,642	6,487,255	6,498,193
Average invested capital	277,404	293,736	289,665
Performance measurements: [Abstract]
Return on average assets	0.56%	1.00%	1.22%
Return on average invested capital	13.30%	21.99%	27.28%
Efficiency ratio	56.58%	51.30%	49.60%
Operating Segments [Member] \| Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	23,826	25,478	27,647
Net interest revenue (expense) from internal sources	20,578	20,061	21,456
Net interest revenue	44,404	45,539	49,103
Provision for credit losses	213	1,275	2,284
Net interest revenue after provision for credit losses	44,191	44,264	46,819
Other operating revenue	239,045	211,655	197,306
Operating expense	216,770	197,890	177,423
Net direct contribution	66,466	58,029	66,702
Corporate expense allocations	31,375	29,993	30,525
Net income before taxes	35,091	28,036	36,177
Federal and state income taxes	13,650	10,906	14,073
Net income	21,441	17,130	22,104
Net income attributable to non-controlling interests	0	0	0
Net income attributable to BOK Financial Corp. shareholders	21,441	17,130	22,104
Average assets	4,518,511	4,556,132	4,357,641
Average invested capital	193,784	203,914	184,707
Performance measurements: [Abstract]
Return on average assets	0.52%	0.40%	0.52%
Return on average invested capital	12.07%	9.00%	12.26%
Efficiency ratio	75.90%	76.37%	71.19%
Corporate, Non-Segment [Member] \| Funds Management and Other [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	163,771	184,885	211,338
Net interest revenue (expense) from internal sources	(8,814)	(3,324)	679
Net interest revenue	154,957	181,561	212,017
Provision for credit losses	1,829	(30,335)	(44,335)
Net interest revenue after provision for credit losses	153,128	211,896	256,352
Other operating revenue	3,095	14,275	22,564
Operating expense	232,922	263,325	263,946
Net direct contribution	(76,699)	(37,154)	14,970
Corporate expense allocations	(139,753)	(134,863)	(139,094)
Net income before taxes	63,054	97,709	154,064
Federal and state income taxes	(8,018)	10,054	37,497
Net income	71,072	87,655	116,567
Net income attributable to non-controlling interests	3,044	2,322	2,933
Net income attributable to BOK Financial Corp. shareholders	68,028	85,333	113,634
Average assets	5,540,197	5,951,472	5,589,171
Average invested capital	$ 1,793,190	$ 1,606,715	$ 1,549,547

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