Consolidated Statements of Earnings (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Interest revenue [Abstract]
Loans	$ 502,753	$ 498,600	$ 513,429
Residential mortgage loans held for sale	10,143	8,505	8,185
Trading securities	1,945	1,962	1,419
Investment securities, Taxable securities	13,183	14,260	16,848
Investment securities, Tax-exempt securities	5,708	4,781	3,577
Total investment securities	18,891	19,041	20,425
Available for sale securities, Taxable securities	182,923	204,830	237,226
Available for sale securities, Tax-exempt securities	2,184	2,380	2,487
Total available for sale securities	185,107	207,210	239,713
Fair value option securities	3,611	3,907	8,464
Restricted equity securities	7,040	5,071	2,291
Interest-bearing cash and cash equivalents	2,749	1,075	945
Total interest revenue	732,239	745,371	794,871
Interest expense [Abstract]
Deposits	50,683	55,564	67,013
Borrowed funds	7,672	6,589	6,531
Subordinated debentures	8,690	8,741	13,778
Total interest expense	67,045	70,894	87,322
Net interest revenue	665,194	674,477	707,549
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 [Abstract]
Brokerage and trading revenue	134,437	125,478	126,930
Transaction card revenue	123,689	116,823	107,985
Fiduciary and asset management revenue	115,652	96,082	80,053
Deposit service charges and fees	90,911	95,110	98,917
Mortgage banking revenue	109,093	121,934	169,302
Bank-owned life insurance	9,086	10,155	11,089
Other revenue	38,451	38,262	34,604
Total fees and commissions	621,319	603,844	628,880
Loss on assets, net	(6,346)	(925)	(1,415)
Gain (loss) on derivatives, net	2,776	(4,367)	(301)
Gain (loss) on fair value option securities, net	10,189	(15,212)	9,230
Change in fair value of mortgage servicing rights	(16,445)	22,720	(9,210)
Gain on available for sale securities, net	1,539	10,720	33,845
Total other-than-temporary impairment losses	(373)	(2,574)	(1,144)
Portion of loss recognized in (reclassified from) other comprehensive income	0	266	(6,207)
Net impairment losses recognized in earnings	(373)	(2,308)	(7,351)
Total other operating revenue	612,659	614,472	653,678
Other operating expense [Abstract]
Personnel	476,931	505,225	491,033
Business promotion	26,649	22,598	23,338
Charitable contributions to BOKF Foundation	4,267	2,062	2,062
Professional fees and services	44,440	32,552	34,015
Net occupancy and equipment	77,232	69,773	66,726
Insurance	18,578	16,122	15,356
Data processing and communications	117,049	106,075	98,904
Printing, postage and supplies	13,518	13,885	14,228
Net losses and operating expenses of repossessed assets	6,019	5,160	20,528
Amortization of intangible assets	3,965	3,428	2,927
Mortgage banking costs	29,881	31,088	44,334
Other expense	28,993	32,652	26,912
Total other operating expense	847,522	840,620	840,363
Net income before taxes	430,331	476,229	542,864
Federal and state income taxes	134,852	157,298	188,740
Net income	295,479	318,931	354,124
Net income attributable to non-controlling interests	3,044	2,322	2,933
Net income attributable to BOK Financial Corp. shareholders	$ 292,435	$ 316,609	$ 351,191
Earnings per share: [Abstract]
Basic (in dollars per share)	$ 4.23	$ 4.61	$ 5.15
Diluted (in dollars per share)	$ 4.22	$ 4.59	$ 5.13
Average shares used in computation: [Abstract]
Basic (in shares)	68,394,194	67,988,897	67,684,043
Diluted (in shares)	68,544,770	68,205,519	67,964,940
Dividends declared per share (in dollars per share)	$ 1.62	$ 1.54	$ 2.47