Federal and State Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Amount [Abstract]
Federal statutory tax	$ 42,316	$ 41,136	$ 82,033	$ 81,904
Tax exempt revenue	(2,322)	(2,098)	(4,568)	(4,090)
Effect of state income taxes, net of federal benefit	2,510	2,457	5,125	5,327
Utilization of tax credits: [Abstract]
Low-income housing tax credit, net of amortization	(1,055)	160	(1,812)	(832)
Other tax credits	(522)	(674)	(1,043)	(1,055)
Bank-owned life insurance	(828)	(784)	(1,632)	(1,552)
Charitable contributions to BOKF Foundation	0	0	0	(427)
Other, net	531	606	911	965
Total	$ 40,630	$ 40,803	$ 79,014	$ 80,240
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)	(1.90%)	(1.80%)	(1.90%)	(1.70%)
Effect of state income taxes, net of federal benefit (in hundredths)	2.10%	2.20%	2.20%	2.30%
Utilization of tax credits: [Abstract]
Low-income housing tax credit, net of amortization (in hundreths)	(0.90%)	0.10%	(0.80%)	(0.40%)
Other tax credits (in hundreths)	(0.40%)	(0.60%)	(0.40%)	(0.50%)
Bank-owned life insurance (in hundredths)	(0.70%)	(0.70%)	(0.70%)	(0.70%)
Charitable contribution to BOKF Foundation (in hundredths)	0.00%	0.00%	0.00%	(0.20%)
Other, net (in hundredths)	0.40%	0.50%	0.30%	0.50%
Total (in hundredths)	33.60%	34.70%	33.70%	34.30%