Other Borrowings (Details) (USD $)	12 Months Ended					0 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Jun. 05, 2015	May 15, 2017	Jun. 01, 2015
Other Borrowings [Line Items]
Balance	$ 3,726,277,000		$ 3,069,690,000		$ 3,053,854,000
Average balance	3,699,621,000		3,719,768,000		3,104,724,000
Weighted Average Interest Rate During Period	0.43%		0.40%		0.65%
US Agency Securities [Member]
Repurchase Agreements, Security Sold/Maturity [Abstract]
Amortized Cost	1,185,345,000		1,085,893,000
Market Value	1,192,361,000		1,075,821,000
Repurchase Liability	1,187,445,000	[1]	813,624,000	[1]
Average Rate (in hundredths)	0.04%		0.05%
US Agency Securities [Member] | Overnight [Member]
Repurchase Agreements, Security Sold/Maturity [Abstract]
Amortized Cost	1,185,345,000		1,085,893,000
Market Value	1,192,361,000		1,075,821,000
Repurchase Liability	1,187,445,000	[1]	813,624,000	[1]
Average Rate (in hundredths)	0.04%		0.05%
US Agency Securities [Member] | Long-term [Member]
Repurchase Agreements, Security Sold/Maturity [Abstract]
Amortized Cost	0		0
Market Value	0		0
Repurchase Liability	0	[1]	0	[1]
Average Rate (in hundredths)	0.00%		0.00%
Parent Company and other non-bank subsidiaries [Member]
Other Borrowings [Line Items]
Balance	0		0		10,500,000
Average balance	0		326,000		394,000
Weighted Average Interest Rate During Period	0.00%		0.00%		1.11%
Other borrowings, Maturities [Abstract]
2015	0
2016	0
2017	0
2018	0
2019	0
Thereafter	0
Parent Company and other non-bank subsidiaries [Member] | Senior Unsecured Revolving Credit Facility [Member]
Other Borrowings [Line Items]
Balance	0		0
Other borrowings, Other Disclosures [Abstract]
Maturity date						Jun. 05, 2015
Senior Unsecured Revolving Credit Facility [Abstract]
Senior unsecured revolving credit facility, borrowing capacity	100,000,000
Senior unsecured revolving credit facility, revolving period	364
Senior unsecured revolving credit facility, interest rate description	defined base rate minus 1.25% or LIBOR plus 1.00% based upon the Company’s option
Senior unsecured revolving credit facility, Term loan, interest rate description	defined base rate minus 1.25% or LIBOR plus 1.25%
Senior unsecured revolving credit facility, unused capacity, commitment fee percentage	0.20%
Parent Company and other non-bank subsidiaries [Member] | Other Borrowings [Member]
Other Borrowings [Line Items]
Balance	0		0		10,500,000
Weighted Average Interest Rate	0.00%		0.00%		1.50%
Average balance	0		326,000		394,000
Weighted Average Interest Rate During Period	0.00%		0.00%		1.11%
Maximum Outstanding At Any Month End	0		0		10,500,000
Subsidiary Bank [Member]
Other Borrowings [Line Items]
Balance	3,726,277,000		3,069,690,000		3,043,354,000
Average balance	3,699,621,000		3,719,442,000		3,104,330,000
Weighted Average Interest Rate During Period	0.43%		0.41%		0.65%
Other borrowings, Maturities [Abstract]
2015	3,484,519,000
2016	525,000
2017	226,732,000
2018	575,000
2019	575,000
Thereafter	13,351,000
Subsidiary Bank [Member] | Funds Purchased [Member]
Other Borrowings [Line Items]
Balance	57,031,000		868,081,000		1,167,416,000
Weighted Average Interest Rate	0.05%		0.04%		0.05%
Average balance	494,220,000		866,062,000		1,512,711,000
Weighted Average Interest Rate During Period	0.07%		0.10%		0.14%
Maximum Outstanding At Any Month End	1,548,676,000		997,536,000		1,810,793,000
Other borrowings, Other Disclosures [Abstract]
Number of days to maturity, minimum	1 day
Number of days to maturity, maximum	90 days
Subsidiary Bank [Member] | Repurchase Agreements [Member]
Other Borrowings [Line Items]
Balance	1,187,489,000		813,454,000		887,030,000
Weighted Average Interest Rate	0.04%		0.05%		0.07%
Average balance	928,767,000		811,996,000		1,072,650,000
Weighted Average Interest Rate During Period	0.06%		0.06%		0.09%
Maximum Outstanding At Any Month End	1,187,489,000		881,033,000		1,272,151,000
Other borrowings, Other Disclosures [Abstract]
Number of days to maturity, maximum	90 days
Accrued interest payable	0		0
Subsidiary Bank [Member] | Other Borrowings [Member]
Other Borrowings [Line Items]
Balance	2,133,774,000		1,040,353,000		641,275,000
Average balance	1,928,742,000		1,693,667,000		155,271,000
Weighted Average Interest Rate During Period	0.35%
Subsidiary Bank [Member] | Federal Home Loan Bank Advances [Member]
Other Borrowings [Line Items]
Balance	2,103,400,000		1,005,650,000		604,897,000
Weighted Average Interest Rate	0.25%		0.19%		0.23%
Average balance	1,894,966,000		1,661,424,000		104,925,000
Weighted Average Interest Rate During Period	0.24%		0.20%		0.31%
Maximum Outstanding At Any Month End	3,453,400,000		2,451,197,000		604,897,000
Other borrowings, Other Disclosures [Abstract]
Federal Home Loan Banks, Letters of credit issued to secure public funds	315,000,000
Unused credit available pursuant to the FHLB's collateral policies	1,900,000,000
Subsidiary Bank [Member] | GNMA Repurchase Liability [Member]
Other Borrowings [Line Items]
Balance	14,298,000		18,113,000		20,046,000
Weighted Average Interest Rate	5.05%		5.50%		5.44%
Average balance	17,343,000		15,741,000		33,769,000
Weighted Average Interest Rate During Period	5.20%		5.43%		5.41%
Maximum Outstanding At Any Month End	24,980,000		21,055,000		47,840,000
Subsidiary Bank [Member] | Other [Member]
Other Borrowings [Line Items]
Balance	16,076,000		16,590,000		16,332,000
Weighted Average Interest Rate	2.73%		2.73%		2.79%
Average balance	16,433,000		16,502,000		16,577,000
Weighted Average Interest Rate During Period	2.32%		2.54%		2.91%
Maximum Outstanding At Any Month End	16,582,000		17,092,000		16,761,000
Subsidiary Bank [Member] | Subordinated Debentures [Member]
Other Borrowings [Line Items]
Balance	347,983,000		347,802,000		347,633,000
Weighted Average Interest Rate	2.35%		2.35%		2.40%
Average balance	347,892,000		347,717,000		363,699,000
Weighted Average Interest Rate During Period	2.50%		2.51%		3.79%
Maximum Outstanding At Any Month End	347,983,000		347,802,000		398,897,000
Subsidiary Bank [Member] | Subordinated Debentures, 2007 Issuance [Member]
Other Borrowings [Line Items]
Balance	227,000,000
Other borrowings, Other Disclosures [Abstract]
Amount of debt issuance	250,000,000
Maturity date							May 15, 2017
Interest rate description	fixed rate of 5.75% through May 14, 2012 and is based on a floating rate of three-month LIBOR plus 0.69% thereafter
Subsidiary Bank [Member] | Subordinated Debentures, 2005 Issuance [Member]
Other Borrowings [Line Items]
Balance	122,000,000
Weighted Average Interest Rate	5.56%
Other borrowings, Other Disclosures [Abstract]
Amount of debt issuance	$ 150,000,000
Maturity date								Jun. 01, 2015

[1] 1 BOK Financial maintains control over the securities underlying overnight repurchase agreements and generally transfers control over securities underlying longer-term dealer repurchase agreements to the respective counterparty.