Parent Company Only Financial Statements Parent Company Only Financial Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets [Abstract]
Cash and cash equivalents	$ 2,475,842	$ 1,087,213	$ 1,286,239	$ 2,643,599	$ 2,475,842	$ 1,087,213	$ 1,286,239
Available for sale securities				9,042,733	8,978,945
Other assets				249,112	195,252
Total assets				31,476,128	29,089,698
Liabilities and Shareholders' Equity [Abstract]
Other liabilities				124,284	121,051
Total liabilities				28,208,489	25,753,492
Shareholders' equity: [Abstract]
Common stock				4	4
Capital surplus				982,009	954,644
Retained earnings				2,704,121	2,530,837
Treasury stock				(477,165)	(239,979)
Accumulated other comprehensive income				21,587	56,673	(25,623)	149,920
Total shareholders' equity				3,230,556	3,302,179
Total liabilities and shareholders' equity				31,476,128	29,089,698
Income Statement [Abstract]
Other revenue	40,579	38,451	38,262
Interest expense	63,474	67,045	70,894
Charitable contributions to BOKF Foundation	796	4,267	2,062
Professional fees and services	40,123	44,440	32,552
Other operating expense	904,564	847,522	840,620
Federal and state income taxes	139,384	144,151	163,098
Net income attributable to BOK Financial Corp. shareholders	288,565	292,435	316,609
Cash Flows From Operating Activities: [Abstract]
Net income	292,259	295,479	318,931
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Tax effect from equity compensation, net	(925)	(8,258)	(2,210)
Change in other assets	20,244	(77,907)	(76,257)
Change in other liabilities	15,756	1,007	(13,735)
Net cash provided by operating activities	295,010	(36,630)	736,320
Cash Flows From Investing Activities: [Abstract]
Proceeds from sales of available for sale securities	1,600,380	2,664,740	2,436,093
Acquisitions, net of cash acquired	(18,098)	(21,898)	(7,500)
Net cash used in investing activities	(2,001,304)	(434,020)	437,029
Cash Flows From Financing Activities: [Abstract]
Issuance of common and treasury stock, net	6,711	4,472	16,566
Tax effect from equity compensation, net	925	8,258	2,210
Dividends paid	(115,281)	(111,026)	(104,722)
Repurchase of common stock	(229,540)	(12,337)	0
Net cash used in financing activities	1,874,051	1,859,279	(1,372,375)
Net increase (decrease) in cash and cash equivalents	167,757	1,388,629	(199,026)
Cash and cash equivalents at beginning of period	2,475,842	1,087,213	1,286,239
Cash and cash equivalents at end of period	2,643,599	2,475,842	1,087,213
Cash paid for interest	66,091	65,721	69,830
Issuance of shares in settlement of deferred compensation, net		8,352
Parent Company [Member]
Assets [Abstract]
Cash and cash equivalents	510,668	561,297	457,514	282,169	510,668	$ 561,297	$ 457,514
Available for sale securities				20,150	24,794
Investments in subsidiaries				2,933,081	2,774,276
Other assets				1,534	1,637
Total assets				3,236,934	3,311,375
Liabilities and Shareholders' Equity [Abstract]
Other liabilities				6,378	9,196
Total liabilities				6,378	9,196
Shareholders' equity: [Abstract]
Common stock				4	4
Capital surplus				982,009	954,644
Retained earnings				2,704,121	2,530,837
Treasury stock				(477,165)	(239,979)
Accumulated other comprehensive income				21,587	56,673
Total shareholders' equity				3,230,556	3,302,179
Total liabilities and shareholders' equity				$ 3,236,934	$ 3,311,375
Income Statement [Abstract]
Dividends, interest and fees received from subsidiaries	150,308	75,412	225,340
Other revenue	1,279	1,572	3,341
Total revenue	151,587	76,984	228,681
Interest expense	131	293	292
Charitable contributions to BOKF Foundation	0	2,420	2,062
Professional fees and services	378	600	811
Other operating expense	1,864	1,556	1,210
Total expenses	2,373	4,869	4,375
Income before taxes and equity in undistributed income of subsidiaries	149,214	72,115	224,306
Federal and state income taxes	(375)	(1,702)	(1,578)
Income before equity in undistributed earnings of subsidiaries	149,589	73,817	225,884
Equity in undistributed income of subsidiaries	138,976	218,618	90,725
Net income attributable to BOK Financial Corp. shareholders	288,565	292,435	316,609
Cash Flows From Operating Activities: [Abstract]
Net income	288,565	292,435	316,609
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Equity in undistributed income of subsidiaries	(138,976)	(218,618)	(90,725)
Tax effect from equity compensation, net	(925)	(8,258)	(2,210)
Change in other assets	49	8,726	(8,308)
Change in other liabilities	(2,818)	1,055	4,263
Net cash provided by operating activities	145,895	75,340	219,629
Cash Flows From Investing Activities: [Abstract]
Proceeds from sales of available for sale securities	4,760	0	13,600
Investment in subsidiaries	(41,969)	(15,336)	(36,000)
Acquisitions, net of cash acquired	0	0	(7,500)
Net cash used in investing activities	(37,209)	(15,336)	(29,900)
Cash Flows From Financing Activities: [Abstract]
Issuance of common and treasury stock, net	6,711	4,472	16,566
Tax effect from equity compensation, net	925	8,258	2,210
Dividends paid	(115,281)	(111,026)	(104,722)
Repurchase of common stock	(229,540)	(12,337)	0
Net cash used in financing activities	(337,185)	(110,633)	(85,946)
Net increase (decrease) in cash and cash equivalents	(228,499)	(50,629)	103,783
Cash and cash equivalents at beginning of period	510,668	561,297	457,514
Cash and cash equivalents at end of period	282,169	510,668	561,297
Cash paid for interest	131	293	292
Issuance of shares in settlement of deferred compensation, net	$ 0	$ 8,352	$ 0