Federal and State Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Amount [Abstract]
Federal statutory tax	$ 37,802	$ 38,333	$ 117,778	$ 128,446
Tax exempt revenue	(2,164)	(1,860)	(6,254)	(5,405)
Effect of state income taxes, net of federal benefit	2,328	2,072	7,655	8,572
Utilization of tax credits	(2,746)	(1,669)	(8,213)	(5,217)
Bank-owned life insurance	(806)	(871)	(2,358)	(2,749)
Reduction of tax accrual	(2,281)	(1,400)	(2,281)	(1,400)
Charitable contributions to BOKF Foundation	0	(1,115)	(427)	(1,115)
Other, net	(254)	(29)	710	848
Total	$ 31,879	$ 33,461	$ 106,610	$ 121,980
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory tax (in hundredths)	35.00%	35.00%	35.00%	35.00%
Tax exempt revenue (in hundredths)	(2.00%)	(2.00%)	(2.00%)	(1.00%)
Effect of state income taxes, net of federal benefit (in hundredths)	3.00%	2.00%	3.00%	2.00%
Utilization of tax credits (in hundredths)	(3.00%)	(1.00%)	(2.00%)	(1.00%)
Bank-owned life insurance (in hundredths)	(1.00%)	(1.00%)	(1.00%)	(1.00%)
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Percent	(2.00%)	(1.00%)	(1.00%)	(1.00%)
Charitable contribution to BOKF Foundation (in hundredths)	0.00%	(1.00%)	0.00%	0.00%
Other, net (in hundredths)	0.00%	0.00%	0.00%	0.00%
Total (in hundredths)	30.00%	31.00%	32.00%	33.00%