Parent Company Only Financial Statements Parent Company Only Financial Statements (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets [Abstract]
Cash and cash equivalents	$ 2,475,842	$ 1,087,213	$ 1,286,239
Available for sale securities	8,978,945	10,147,162
Other assets	195,252	359,894
Total assets	29,089,698	27,015,432
Liabilities and Equity [Abstract]
Other liabilities	121,051	133,647
Total liabilities	25,753,492	23,960,459
Shareholders' equity: [Abstract]
Common stock	4	4
Capital surplus	954,644	898,586
Retained earnings	2,530,837	2,349,428
Treasury stock	(239,979)	(202,346)
Accumulated other comprehensive income (loss)	56,673	(25,623)	149,920	128,979
Total shareholders' equity	3,302,179	3,020,049
Total liabilities and equity	29,089,698	27,015,432
Income Statement [Abstract]
Other revenue	38,451	38,262	34,604
Net impairment losses recognized in earnings	(373)	(2,308)	(7,351)
Interest expense	67,045	70,894	87,322
Charitable contributions to BOKF Foundation	4,267	2,062	2,062
Professional fees and services	44,440	32,552	34,015
Other operating expense	847,522	840,620	840,363
Federal and state income taxes	134,852	157,298	188,740
Net income attributable to BOK Financial Corp. shareholders	292,435	316,609	351,191
Cash Flows From Operating Activities: [Abstract]
Net income	295,479	318,931	354,124
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Tax effect from equity compensation, net	(8,258)	(2,210)	(120)
Change in other assets	(77,907)	(76,257)	(10,999)
Change in other liabilities	1,007	(13,735)	(3,729)
Net cash provided by operating activities	(36,630)	736,320	591,550
Cash Flows From Investing Activities: [Abstract]
Purchases of available for sale securities	(3,045,077)	(4,287,146)	(7,334,843)
Proceeds from sales of available for sale securities	2,664,740	2,436,093	1,744,662
Acquisitions, net of cash acquired	(21,898)	(7,500)	(23,615)
Net cash used in investing activities	(434,020)	437,029	(2,368,347)
Cash Flows From Financing Activities: [Abstract]
Issuance of common and treasury stock, net	4,472	16,566	14,650
Tax effect from equity compensation, net	8,258	2,210	120
Dividends paid	(111,026)	(104,722)	(166,982)
Repurchase of common stock	(12,337)	0	(20,558)
Net cash used in financing activities	1,859,279	(1,372,375)	2,076,671
Net increase (decrease) in cash and cash equivalents	1,388,629	(199,026)	299,874
Cash and cash equivalents at beginning of period	1,087,213	1,286,239	986,365
Cash and cash equivalents at end of period	2,475,842	1,087,213	1,286,239
Cash paid for interest	65,721	69,830	90,137
Issuance of shares in settlement of deferred compensation, net	8,352	0	0
Parent Company [Member]
Assets [Abstract]
Cash and cash equivalents	510,668	561,297	457,514
Available for sale securities	24,794	27,526
Investments in subsidiaries	2,774,276	2,426,495
Other assets	1,637	12,872
Total assets	3,311,375	3,028,190
Liabilities and Equity [Abstract]
Other liabilities	9,196	8,141
Total liabilities	9,196	8,141
Shareholders' equity: [Abstract]
Common stock	4	4
Capital surplus	954,644	898,586
Retained earnings	2,530,837	2,349,428
Treasury stock	(239,979)	(202,346)
Accumulated other comprehensive income (loss)	56,673	(25,623)
Total shareholders' equity	3,302,179	3,020,049
Total liabilities and equity	3,311,375	3,028,190
Income Statement [Abstract]
Dividends, interest and fees received from subsidiaries	75,412	225,340	275,330
Other revenue	1,572	3,341	2,295
Net impairment losses recognized in earnings	0	0	(1,099)
Total revenue	76,984	228,681	276,526
Interest expense	293	292	269
Charitable contributions to BOKF Foundation	2,420	2,062	2,062
Professional fees and services	600	811	765
Other operating expense	1,556	1,210	1,037
Total expenses	4,869	4,375	4,133
Income before taxes and equity in undistributed income of subsidiaries	72,115	224,306	272,393
Federal and state income taxes	(1,702)	(1,578)	(1,706)
Income before equity in undistributed earnings of subsidiaries	73,817	225,884	274,099
Equity in undistributed income of subsidiaries	218,618	90,725	77,092
Net income attributable to BOK Financial Corp. shareholders	292,435	316,609	351,191
Cash Flows From Operating Activities: [Abstract]
Net income	292,435	316,609	351,191
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Equity in undistributed income of subsidiaries	218,618	90,725	77,092
Tax effect from equity compensation, net	(8,258)	(2,210)	(120)
Change in other assets	8,726	(8,308)	4,237
Change in other liabilities	1,055	4,263	(4,965)
Net cash provided by operating activities	75,340	219,629	273,251
Cash Flows From Investing Activities: [Abstract]
Purchases of available for sale securities	0	0	(5,343)
Proceeds from sales of available for sale securities	0	13,600	4,781
Investment in subsidiaries	(15,336)	(36,000)	(9,100)
Acquisitions, net of cash acquired	0	(7,500)	(20,000)
Net cash used in investing activities	(15,336)	(29,900)	(29,662)
Cash Flows From Financing Activities: [Abstract]
Issuance of common and treasury stock, net	4,472	16,566	14,650
Tax effect from equity compensation, net	8,258	2,210	120
Dividends paid	(111,026)	(104,722)	(166,982)
Repurchase of common stock	(12,337)	0	(20,558)
Net cash used in financing activities	(110,633)	(85,946)	(172,770)
Net increase (decrease) in cash and cash equivalents	(50,629)	103,783	70,819
Cash and cash equivalents at beginning of period	561,297	457,514	386,695
Cash and cash equivalents at end of period	510,668	561,297	457,514
Cash paid for interest	293	292	269
Issuance of shares in settlement of deferred compensation, net	$ 8,352	$ 0	$ 0