Commitments and Contingent Liabilities (Details)	6 Months Ended
	Jun. 30, 2018 USD ($) shares
BOKF Equity, LLC [Member]
Litigation Settlement [Abstract]
Number of Private Equity Funds of which the Entity is a General Partner	2
Contingent Obligations For Additional Investments in Private Equity Funds	$ 3,400,000
Judicial Ruling [Member] | Misuse of Revenues Pledged to Municipal Bonds [Member]
Litigation Settlement [Abstract]
Outstanding principal, accrued interest and other amounts required by bond documents	40,000,000
Disgorged fees	1,067,721
Litigation Settlement, Amount Awarded to Other Party	$ 600,000
Pending Litigation [Member] | Misuse of Revenues Pledged to Municipal Bonds [Member]
Litigation Settlement [Abstract]
Loss Contingency, Number of Plaintiffs	2
Alleged total of judgment against nursing home operator	$ 8,000,000
Pending Litigation [Member] | Bank Participation in Fraudulent Sale of Securities by Principals [Member]
Litigation Settlement [Abstract]
Loss Contingency, Number of Plaintiffs	19
Pending Litigation [Member] | Purchase of facilities from principals subject to SEC New Jersey proceedings [Member]
Litigation Settlement [Abstract]
Outstanding principal, accrued interest and other amounts required by bond documents	$ 60,000,000
Number of individuals who purchased facilities from the principals subject to SEC New Jersey proceedings	2
Number of principals in SEC New Jersey proceedings	2
Visa Membership [Member]
Loss Contingencies [Line Items]
Number of Visa Class B Shares Owned by Entity (in shares) | shares	252,233
Number of Visa Class A Shares Visa Class B Shares Are Convertible To (in shares) | shares	411,089