XML 9 R1.htm IDEA: XBRL DOCUMENT v3.21.1
Document and Entity Information Document
Apr. 29, 2021
Oct. 29, 2020
Entity Information [Line Items]    
Document Type 8-K  
Document Period End Date Apr. 29, 2021  
Entity Registrant Name Cullen/Frost Bankers, Inc.  
Entity Incorporation, State or Country Code TX  
Entity File Number 001-13221  
Entity Tax Identification Number 74-1751768  
Entity Address, Address Line One 111 W. Houston Street,  
Entity Address, City or Town San Antonio,  
Entity Address, State or Province TX  
Entity Address, Postal Zip Code 78205  
City Area Code (210)  
Local Phone Number 220-4011  
Written Communications false  
Soliciting Material false  
Pre-commencement Tender Offer false  
Pre-commencement Issuer Tender Offer false  
Entity Emerging Growth Company false  
Amendment Flag   false
Entity Central Index Key   0000039263
Common Stock | NEW YORK STOCK EXCHANGE, INC.    
Entity Information [Line Items]    
Title of 12(b) Security Common Stock, $.01 Par Value  
Trading Symbol CFR  
Security Exchange Name NYSE  
Series B Preferred Stock | NEW YORK STOCK EXCHANGE, INC.    
Entity Information [Line Items]    
Title of 12(b) Security Depositary Shares, each representing a 1/40th interest in a share of 4.450% Non-Cumulative Perpetual Preferred Stock, Series B  
Trading Symbol CFR.PrB  
Security Exchange Name NYSE