Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Net interest revenue from external sources	$ 201,182	$ 182,572
Net interest revenue (expense) from internal sources	0	0
Net interest revenue	201,182	182,572
Provision for credit losses	0	35,000
Net interest revenue after provision for credit losses	201,182	147,572
Other operating revenue	170,296	157,414
Other operating expense	244,711	242,570
Net direct contribution	126,767	62,416
Gain (loss) on financial instruments, net	0	0
Change in fair value of mortgage servicing rights	0	0
Gain (loss) on repossessed assets, net	0	0
Corporate expense allocations	0	0
Net income before taxes	126,767	62,416
Federal and state income taxes	38,103	21,428
Net income	88,664	40,988
Net income (loss) attributable to non-controlling interests	308	(1,576)
Net income attributable to BOK Financial Corp. shareholders	88,356	42,564
Average assets	32,954,989	31,508,471
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	134,704	116,637
Net interest revenue (expense) from internal sources	(16,793)	(14,632)
Net interest revenue	117,911	102,005
Provision for credit losses	(1,462)	21,572
Net interest revenue after provision for credit losses	119,373	80,433
Other operating revenue	46,270	45,108
Other operating expense	52,436	56,070
Net direct contribution	113,207	69,471
Gain (loss) on financial instruments, net	38	0
Change in fair value of mortgage servicing rights	0	0
Gain (loss) on repossessed assets, net	(5)	(82)
Corporate expense allocations	8,631	8,744
Net income before taxes	104,609	60,645
Federal and state income taxes	40,693	23,591
Net income	63,916	37,054
Net income (loss) attributable to non-controlling interests	0	0
Net income attributable to BOK Financial Corp. shareholders	63,916	37,054
Average assets	17,438,776	16,969,015
Operating Segments [Member] | Consumer [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	21,129	21,449
Net interest revenue (expense) from internal sources	10,952	9,353
Net interest revenue	32,081	30,802
Provision for credit losses	1,272	1,702
Net interest revenue after provision for credit losses	30,809	29,100
Other operating revenue	47,306	54,029
Other operating expense	53,532	55,718
Net direct contribution	24,583	27,411
Gain (loss) on financial instruments, net	(1,667)	16,581
Change in fair value of mortgage servicing rights	1,856	(27,988)
Gain (loss) on repossessed assets, net	(136)	153
Corporate expense allocations	16,868	15,978
Net income before taxes	7,768	179
Federal and state income taxes	3,022	70
Net income	4,746	109
Net income (loss) attributable to non-controlling interests	0	0
Net income attributable to BOK Financial Corp. shareholders	4,746	109
Average assets	8,648,562	8,687,289
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	11,485	6,078
Net interest revenue (expense) from internal sources	8,856	7,663
Net interest revenue	20,341	13,741
Provision for credit losses	40	(150)
Net interest revenue after provision for credit losses	20,301	13,891
Other operating revenue	74,158	68,747
Other operating expense	60,410	60,684
Net direct contribution	34,049	21,954
Gain (loss) on financial instruments, net	0	0
Change in fair value of mortgage servicing rights	0	0
Gain (loss) on repossessed assets, net	0	0
Corporate expense allocations	10,672	10,535
Net income before taxes	23,377	11,419
Federal and state income taxes	9,094	4,442
Net income	14,283	6,977
Net income (loss) attributable to non-controlling interests	0	0
Net income attributable to BOK Financial Corp. shareholders	14,283	6,977
Average assets	7,160,849	5,565,047
Corporate, Non-Segment [Member] | Funds Management and Other [Member]
Segment Reporting Information [Line Items]
Net interest revenue from external sources	33,864	38,408
Net interest revenue (expense) from internal sources	(3,015)	(2,384)
Net interest revenue	30,849	36,024
Provision for credit losses	150	11,876
Net interest revenue after provision for credit losses	30,699	24,148
Other operating revenue	2,562	(10,470)
Other operating expense	78,333	70,098
Net direct contribution	(45,072)	(56,420)
Gain (loss) on financial instruments, net	1,629	(16,581)
Change in fair value of mortgage servicing rights	(1,856)	27,988
Gain (loss) on repossessed assets, net	141	(71)
Corporate expense allocations	(36,171)	(35,257)
Net income before taxes	(8,987)	(9,827)
Federal and state income taxes	(14,706)	(6,675)
Net income	5,719	(3,152)
Net income (loss) attributable to non-controlling interests	308	(1,576)
Net income attributable to BOK Financial Corp. shareholders	5,411	(1,576)
Average assets	$ (293,198)	$ 287,120