Commitments and Contingent Liabilities (Details) - Jun. 30, 2015 $ in Millions	USD ($) shares
Parent Company [Member] | Visa Membership [Member]
Loss Contingencies [Line Items]
Number of Visa Class B Shares Owned by Entity (in shares) | shares	251,837
Number of Visa Class A Shares Visa Class B Shares Are Convertible To | shares	415,103
BOKF Equity, LLC [Member]
Loss Contingencies [Line Items]
Number of Private Equity Funds of which the Entity is a General Partner	2
Contingent Obligations For Additional Investments in Private Equity Funds	$ 5.2
Cavanal Hill Funds [Member]
Loss Contingencies [Line Items]
Mutual Fund Investment in US Treasury Securities	1,200.0
Mutual Fund Investment in Cash Management	1,600.0
Mutual Fund Investment in Tax-Free Money Market Funds	$ 214.0
The Net Asset Value of Units in Mutual Funds (per unit)	1.00