Reportable Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 703,354	$ 665,194	$ 674,477
Net interest revenue (expense) from internal sources	0	0	0
Net interest revenue	703,354	665,194	674,477
Provision for credit losses	34,000	0	(27,900)
Net interest revenue after provision for credit losses	669,354	665,194	702,377
Other operating revenue	666,853	621,958	620,272
Operating expense	904,564	847,522	840,620
Net direct contribution	431,643	439,630	482,029
Corporate expense allocations	0	0	0
Net income before taxes	431,643	439,630	482,029
Federal and state income taxes	139,384	144,151	163,098
Net income	292,259	295,479	318,931
Net income attributable to non-controlling interests	3,694	3,044	2,322
Net income attributable to BOK Financial Corp. shareholders	288,565	292,435	316,609
Average assets	30,574,755	27,998,858	27,381,094
Average invested capital	$ 3,336,752	$ 3,176,073	$ 2,975,426
Performance measurements: [Abstract]
Return on average assets	0.94%	1.04%	1.16%
Return on average invested capital	8.65%	9.21%	10.64%
Efficiency ratio	65.34%	64.50%	64.60%
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 439,727	$ 381,687	$ 363,961
Net interest revenue (expense) from internal sources	(50,678)	(43,939)	(51,592)
Net interest revenue	389,049	337,748	312,369
Provision for credit losses	(6,018)	(7,447)	(4,372)
Net interest revenue after provision for credit losses	395,067	345,195	316,741
Other operating revenue	177,522	169,704	163,206
Operating expense	207,394	204,230	192,629
Net direct contribution	365,195	310,669	287,318
Corporate expense allocations	35,680	41,585	44,107
Net income before taxes	329,515	269,084	243,211
Federal and state income taxes	128,181	104,674	94,609
Net income	201,334	164,410	148,602
Net income attributable to non-controlling interests	0	0	0
Net income attributable to BOK Financial Corp. shareholders	201,334	164,410	148,602
Average assets	13,342,585	11,384,782	10,386,502
Average invested capital	$ 1,050,759	$ 946,383	$ 906,717
Performance measurements: [Abstract]
Return on average assets	1.51%	1.45%	1.43%
Return on average invested capital	19.18%	17.40%	16.39%
Efficiency ratio	36.51%	40.06%	40.74%
Operating Segments [Member] | Consumer [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 84,848	$ 81,852	$ 85,813
Net interest revenue (expense) from internal sources	29,824	36,801	39,628
Net interest revenue	114,672	118,653	125,441
Provision for credit losses	6,108	5,477	5,622
Net interest revenue after provision for credit losses	108,564	113,176	119,819
Other operating revenue	216,772	200,815	225,336
Operating expense	213,782	195,770	188,745
Net direct contribution	111,554	118,221	156,410
Corporate expense allocations	74,868	63,006	56,957
Net income before taxes	36,686	55,215	99,453
Federal and state income taxes	14,271	21,479	38,687
Net income	22,415	33,736	60,766
Net income attributable to non-controlling interests	0	0	0
Net income attributable to BOK Financial Corp. shareholders	22,415	33,736	60,766
Average assets	6,713,444	6,584,157	6,520,498
Average invested capital	$ 265,775	$ 277,404	$ 293,736
Performance measurements: [Abstract]
Return on average assets	0.33%	0.51%	0.93%
Return on average invested capital	8.43%	12.16%	20.69%
Efficiency ratio	62.54%	59.14%	53.22%
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 24,770	$ 23,826	$ 25,478
Net interest revenue (expense) from internal sources	21,524	20,578	20,061
Net interest revenue	46,294	44,404	45,539
Provision for credit losses	(891)	213	1,275
Net interest revenue after provision for credit losses	47,185	44,191	44,264
Other operating revenue	250,942	239,045	211,655
Operating expense	230,838	217,049	198,197
Net direct contribution	67,289	66,187	57,722
Corporate expense allocations	39,654	31,465	29,876
Net income before taxes	27,635	34,722	27,846
Federal and state income taxes	10,750	13,507	10,832
Net income	16,885	21,215	17,014
Net income attributable to non-controlling interests	0	0	0
Net income attributable to BOK Financial Corp. shareholders	16,885	21,215	17,014
Average assets	4,689,850	4,518,511	4,556,132
Average invested capital	$ 225,968	$ 215,089	$ 203,914
Performance measurements: [Abstract]
Return on average assets	0.41%	0.51%	0.40%
Return on average invested capital	8.45%	10.77%	8.95%
Efficiency ratio	77.05%	76.00%	76.49%
Corporate, Non-Segment [Member] | Funds Management and Other [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 154,009	$ 177,829	$ 199,225
Net interest revenue (expense) from internal sources	(670)	(13,440)	(8,097)
Net interest revenue	153,339	164,389	191,128
Provision for credit losses	34,801	1,757	(30,425)
Net interest revenue after provision for credit losses	118,538	162,632	221,553
Other operating revenue	21,617	12,394	20,075
Operating expense	252,550	230,473	261,049
Net direct contribution	(112,395)	(55,447)	(19,421)
Corporate expense allocations	(150,202)	(136,056)	(130,940)
Net income before taxes	37,807	80,609	111,519
Federal and state income taxes	(13,818)	4,491	18,970
Net income	51,625	76,118	92,549
Net income attributable to non-controlling interests	3,694	3,044	2,322
Net income attributable to BOK Financial Corp. shareholders	47,931	73,074	90,227
Average assets	5,828,876	5,511,408	5,917,962
Average invested capital	$ 1,794,250	$ 1,737,197	$ 1,571,059