Reportable Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 167,726	$ 162,642
Net interest revenue (expense) from internal sources	0	0
Net interest revenue	167,726	162,642
Provision for credit losses	0	0
Net interest revenue after provision for credit losses	167,726	162,642
Other operating revenue	166,017	138,942
Other operating expense	220,265	185,104
Net direct contribution	113,478	116,480
Corporate expense allocations	0	0
Net income before taxes	113,478	116,480
Federal and state income taxes	38,384	39,437
Net income	75,094	77,043
Net income attributable to non-controlling interests	251	453
Net income attributable to BOK Financial Corp. shareholders	74,843	76,590
Average assets	29,970,704	27,238,768
Average invested capital	3,351,561	3,105,074
Performance measurements: [Abstract]
Return on average assets	1.01%	1.14%
Return on average invested capital	9.06%	10.00%
Efficiency ratio	64.91%	60.06%
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	101,168	90,831
Net interest revenue (expense) from internal sources	(12,555)	(12,275)
Net interest revenue	88,613	78,556
Provision for credit losses	(9,268)	(3,464)
Net interest revenue after provision for credit losses	97,881	82,020
Other operating revenue	42,884	38,686
Other operating expense	50,580	49,290
Net direct contribution	90,185	71,416
Corporate expense allocations	14,825	13,982
Net income before taxes	75,360	57,434
Federal and state income taxes	29,315	22,342
Net income	46,045	35,092
Net income attributable to non-controlling interests	0	0
Net income attributable to BOK Financial Corp. shareholders	46,045	35,092
Average assets	12,654,200	10,933,196
Average invested capital	994,596	898,724
Performance measurements: [Abstract]
Return on average assets	1.48%	1.31%
Return on average invested capital	18.79%	15.92%
Efficiency ratio	38.43%	41.52%
Operating Segments [Member] | Consumer [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	20,725	20,983
Net interest revenue (expense) from internal sources	7,914	9,229
Net interest revenue	28,639	30,212
Provision for credit losses	1,510	1,090
Net interest revenue after provision for credit losses	27,129	29,122
Other operating revenue	56,231	45,414
Other operating expense	55,858	42,626
Net direct contribution	27,502	31,910
Corporate expense allocations	21,064	19,204
Net income before taxes	6,438	12,706
Federal and state income taxes	2,504	4,943
Net income	3,934	7,763
Net income attributable to non-controlling interests	0	0
Net income attributable to BOK Financial Corp. shareholders	3,934	7,763
Average assets	7,292,883	7,058,658
Average invested capital	272,315	282,705
Performance measurements: [Abstract]
Return on average assets	0.22%	0.45%
Return on average invested capital	5.86%	11.14%
Efficiency ratio	60.79%	53.53%
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	5,384	5,838
Net interest revenue (expense) from internal sources	5,654	4,685
Net interest revenue	11,038	10,523
Provision for credit losses	57	(45)
Net interest revenue after provision for credit losses	10,981	10,568
Other operating revenue	62,346	54,261
Other operating expense	55,042	49,248
Net direct contribution	18,285	15,581
Corporate expense allocations	10,946	11,422
Net income before taxes	7,339	4,159
Federal and state income taxes	2,855	1,618
Net income	4,484	2,541
Net income attributable to non-controlling interests	0	0
Net income attributable to BOK Financial Corp. shareholders	4,484	2,541
Average assets	4,828,340	4,621,817
Average invested capital	224,054	199,369
Performance measurements: [Abstract]
Return on average assets	0.42%	0.26%
Return on average invested capital	9.12%	5.95%
Efficiency ratio	74.73%	75.40%
Corporate, Non-Segment [Member] | Funds Management and Other [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	40,449	44,990
Net interest revenue (expense) from internal sources	(1,013)	(1,639)
Net interest revenue	39,436	43,351
Provision for credit losses	7,701	2,419
Net interest revenue after provision for credit losses	31,735	40,932
Other operating revenue	4,556	581
Other operating expense	58,785	43,940
Net direct contribution	(22,494)	(2,427)
Corporate expense allocations	(46,835)	(44,608)
Net income before taxes	24,341	42,181
Federal and state income taxes	3,710	10,534
Net income	20,631	31,647
Net income attributable to non-controlling interests	251	453
Net income attributable to BOK Financial Corp. shareholders	20,380	31,194
Average assets	5,195,281	4,625,097
Average invested capital	$ 1,860,596	$ 1,724,276