Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
NIR (expense) from external sources	$ 205,204	$ 182,612	$ 406,386	$ 365,184
NIR (expense) from internal sources	0	0	0	0
Net interest revenue	205,204	182,612	406,386	365,184
Provision for credit losses	0	20,000	0	55,000
Net interest revenue after provision for credit losses	205,204	162,612	406,386	310,184
Other operating revenue	182,252	185,542	352,548	342,956
Other operating expense	250,885	251,385	495,596	493,955
Net direct contribution	136,571	96,769	263,338	159,185
Gain (loss) on financial instruments, net	0	0	0	0
Change in fair value of mortgage servicing rights	0	0	0	0
Gain (loss) on repossessed assets, net	0	0	0	0
Corporate expense allocations	0	0	0	0
Net income before taxes	136,571	96,769	263,338	159,185
Federal and state income taxes	47,705	30,497	85,808	51,925
Net income	88,866	66,272	177,530	107,260
Net income (loss) attributable to non-controlling interests	719	471	1,027	(1,105)
Net income attributable to BOK Financial Corp. shareholders	88,147	65,801	176,503	108,365
Average assets	32,368,571	31,986,042	32,660,160	31,747,257
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
NIR (expense) from external sources	144,164	118,480	278,868	235,116
NIR (expense) from internal sources	(20,347)	(14,575)	(37,140)	(29,208)
Net interest revenue	123,817	103,905	241,728	205,908
Provision for credit losses	1,228	6,852	(234)	28,423
Net interest revenue after provision for credit losses	122,589	97,053	241,962	177,485
Other operating revenue	55,778	51,497	102,048	96,605
Other operating expense	59,128	52,594	111,565	108,663
Net direct contribution	119,239	95,956	232,445	165,427
Gain (loss) on financial instruments, net	3	0	41	0
Change in fair value of mortgage servicing rights	0	0	0	0
Gain (loss) on repossessed assets, net	1,403	(598)	1,398	(680)
Corporate expense allocations	8,862	8,883	17,493	17,627
Net income before taxes	111,783	86,475	216,391	147,120
Federal and state income taxes	43,484	33,639	84,176	57,230
Net income	68,299	52,836	132,215	89,890
Net income (loss) attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	68,299	52,836	132,215	89,890
Average assets	17,596,273	16,973,663	17,517,960	16,971,339
Operating Segments [Member] | Consumer [Member]
Segment Reporting Information [Line Items]
NIR (expense) from external sources	23,503	22,349	44,632	43,799
NIR (expense) from internal sources	11,837	8,876	22,789	18,229
Net interest revenue	35,340	31,225	67,421	62,028
Provision for credit losses	926	1,318	2,198	3,020
Net interest revenue after provision for credit losses	34,414	29,907	65,223	59,008
Other operating revenue	52,102	57,440	99,408	111,469
Other operating expense	55,709	62,806	109,242	118,524
Net direct contribution	30,807	24,541	55,389	51,953
Gain (loss) on financial instruments, net	5,224	15,045	3,557	31,626
Change in fair value of mortgage servicing rights	(6,943)	(16,283)	(5,087)	(44,271)
Gain (loss) on repossessed assets, net	98	252	(39)	406
Corporate expense allocations	17,039	16,630	33,908	32,608
Net income before taxes	12,147	6,925	19,912	7,106
Federal and state income taxes	4,725	2,694	7,746	2,764
Net income	7,422	4,231	12,166	4,342
Net income (loss) attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	7,422	4,231	12,166	4,342
Average assets	8,845,398	8,774,881	8,747,524	8,731,085
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting Information [Line Items]
NIR (expense) from external sources	10,474	6,271	21,960	12,349
NIR (expense) from internal sources	10,325	7,193	19,181	14,857
Net interest revenue	20,799	13,464	41,141	27,206
Provision for credit losses	(93)	(239)	(53)	(390)
Net interest revenue after provision for credit losses	20,892	13,703	41,194	27,596
Other operating revenue	75,569	75,772	149,727	144,518
Other operating expense	60,615	61,414	121,025	122,098
Net direct contribution	35,846	28,061	69,896	50,016
Gain (loss) on financial instruments, net	0	0	0	0
Change in fair value of mortgage servicing rights	0	0	0	0
Gain (loss) on repossessed assets, net	0	0	0	0
Corporate expense allocations	9,947	10,417	20,619	20,952
Net income before taxes	25,899	17,644	49,277	29,064
Federal and state income taxes	10,075	6,864	19,169	11,306
Net income	15,824	10,780	30,108	17,758
Net income (loss) attributable to non-controlling interests	0	0	0	0
Net income attributable to BOK Financial Corp. shareholders	15,824	10,780	30,108	17,758
Average assets	6,763,093	5,765,390	6,960,872	5,665,218
Funds Management and Other [Member]
Segment Reporting Information [Line Items]
NIR (expense) from external sources	27,063	35,512	60,926	73,920
NIR (expense) from internal sources	(1,815)	(1,494)	(4,830)	(3,878)
Net interest revenue	25,248	34,018	56,096	70,042
Provision for credit losses	(2,061)	12,069	(1,911)	23,947
Net interest revenue after provision for credit losses	27,309	21,949	58,007	46,095
Other operating revenue	(1,197)	833	1,365	(9,636)
Other operating expense	75,433	74,571	153,764	144,670
Net direct contribution	(49,321)	(51,789)	(94,392)	(108,211)
Gain (loss) on financial instruments, net	(5,227)	(15,045)	(3,598)	(31,626)
Change in fair value of mortgage servicing rights	6,943	16,283	5,087	44,271
Gain (loss) on repossessed assets, net	(1,501)	346	(1,359)	274
Corporate expense allocations	(35,848)	(35,930)	(72,020)	(71,187)
Net income before taxes	(13,258)	(14,275)	(22,242)	(24,105)
Federal and state income taxes	(10,579)	(12,700)	(25,283)	(19,375)
Net income	(2,679)	(1,575)	3,041	(4,730)
Net income (loss) attributable to non-controlling interests	719	471	1,027	(1,105)
Net income attributable to BOK Financial Corp. shareholders	(3,398)	(2,046)	2,014	(3,625)
Average assets	$ (836,193)	$ 472,108	$ (566,196)	$ 379,615