Parent Company Only Financial Statements Parent Company Only Financial Statements (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Assets [Abstract]
Cash and cash equivalents at end of period	$ 1,286,239	$ 986,365	$ 1,269,404
Available for sale securities	11,287,221	10,179,365
Other assets	388,355	381,010
Total assets	28,148,631	25,493,946
Liabilities and Equity [Abstract]
Other liabilities	163,711	133,684
Total liabilities	25,154,950	22,707,294
Shareholders' equity: [Abstract]
Common stock	4	4
Capital surplus	859,278	818,817
Retained earnings	2,137,541	1,953,332
Treasury stock	(188,883)	(150,664)
Accumulated other comprehensive income	149,920	128,979	107,839	(10,740)
Total shareholders' equity	2,957,860	2,750,468
Total liabilities and equity	28,148,631	25,493,946
Income Statement [Abstract]
Other revenue	37,827	35,620	30,368
Net impairment losses recognized in earnings	(7,351)	(23,507)	(27,809)
Interest expense	87,322	120,101	142,030
Professional fees and services	34,015	28,798	30,217
Other operating expense	849,573	819,744	750,320
Federal and state income tax	188,740	158,511	123,357
Net income attributable to BOK Financial Corp. shareholders	351,191	285,875	246,754
Cash Flows From Operating Activities:
Net income	354,124	289,824	248,294
Adjustments to net income to cash provided by operating activities [Abstract]
Tax benefit (expense) on exercise of stock options	(120)	(659)	(425)
Change in other assets	(10,999)	(16,469)	(9,023)
Change in other liabilities	(3,429)	(50,198)	59,037
Net cash provided by operating activities	591,850	327,788	365,178
Cash Flows From Investing Activities:
Purchases of available for sale securities	7,334,843	7,504,261	5,565,931
Proceeds from sales of available for sale securities	1,744,662	2,725,760	2,013,620
Acquisitions, net of cash acquired	23,615	0	0
Net cash provided by (used in) investing activities	(2,368,347)	(1,564,144)	42,661
Net Cash Used in Financing Activities [Abstract]
Issuance of common and treasury stock, net	14,650	14,541	8,552
Dividends paid	166,982	76,423	66,557
Repurchase of common stock	20,558	26,446	0
Net cash used in financing activities	2,076,671	953,317	(59,651)
Net increase in cash and cash equivalents	299,874	(283,039)	348,188
Cash and cash equivalents at beginning of period	986,365	1,269,404	921,216
Cash and cash equivalents at end of period	1,286,239	986,365	1,269,404
Cash paid for interest	90,137	122,166	144,095
Parent Company [Member]
Assets [Abstract]
Cash and cash equivalents at end of period	457,514	386,695	207,453
Available for sale securities	44,881	40,766
Investments in and Advances to Affiliates, at Fair Value	2,464,729	2,317,900
Other assets	4,324	8,682
Total assets	2,971,448	2,754,043
Liabilities and Equity [Abstract]
Other liabilities	13,588	3,575
Total liabilities	13,588	3,575
Shareholders' equity: [Abstract]
Common stock	4	4
Capital surplus	859,278	818,817
Retained earnings	2,137,541	1,953,332
Treasury stock	(188,883)	(150,664)
Accumulated other comprehensive income	149,920	128,979
Total shareholders' equity	2,957,860	2,750,468
Total liabilities and equity	2,971,448	2,754,043
Income Statement [Abstract]
Dividends, interest and fees received from subsidiaries	275,330	270,474	280,125
Other revenue	2,295	2,128	1,883
Net impairment losses recognized in earnings	(1,099)	(2,098)	(1,679)
Total revenue	276,526	270,504	280,329
Interest expense	269	354	507
Professional fees and services	765	538	795
Other operating expense	3,099	7,688	(47)
Total expenses	4,133	8,580	1,255
Income before taxes and equity in undistributed income of subsidiaries	272,393	261,924	279,074
Federal and state income tax	(1,706)	(3,169)	415
Income before equity in undistributed earnings of subsidiaries	274,099	265,093	278,659
Equity in undistributed income of subsidiaries	77,092	20,782	(31,905)
Net income attributable to BOK Financial Corp. shareholders	351,191	285,875	246,754
Cash Flows From Operating Activities:
Net income	351,191	285,875	246,754
Adjustments to net income to cash provided by operating activities [Abstract]
Equity in undistributed income of subsidiaries	(77,092)	(20,782)	31,905
Tax benefit (expense) on exercise of stock options	120	659	(425)
Change in other assets	4,237	15,249	20,713
Change in other liabilities	(5,085)	(18,884)	(20,216)
Net cash provided by operating activities	273,371	262,117	278,731
Cash Flows From Investing Activities:
Purchases of available for sale securities	(5,343)	(3,797)	(10,669)
Proceeds from sales of available for sale securities	4,781	16,500	0
Investment in subsidiaries	(9,100)	(7,250)	(21,692)
Acquisitions, net of cash acquired	(20,000)	0	0
Net cash provided by (used in) investing activities	(29,662)	5,453	(32,361)
Net Cash Used in Financing Activities [Abstract]
Issuance of common and treasury stock, net	14,650	14,541	8,552
Dividends paid	(166,982)	(76,423)	(66,557)
Repurchase of common stock	(20,558)	(26,446)	0
Net cash used in financing activities	(172,890)	(88,328)	(58,005)
Net increase in cash and cash equivalents	70,819	179,242	188,365
Cash and cash equivalents at beginning of period	386,695	207,453	19,088
Cash and cash equivalents at end of period	457,514	386,695	207,453
Cash paid for interest	$ 269	$ 354	$ 507