XML 12 R1.htm IDEA: XBRL DOCUMENT v3.25.2
Cover Page - shares
 6 Months Ended
Jun. 30, 2025
Jul. 31, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2025  
Document Transition Report false  
Entity File Number 001-31940  
Entity Registrant Name FNB CORP/PA/  
Entity Incorporation, State or Country Code PA  
Entity Tax Identification Number 25-1255406  
Entity Address, Address Line One 626 Washington Place,  
Entity Address, City or Town Pittsburgh,  
Entity Address, State or Province PA  
Entity Address, Postal Zip Code 15219  
City Area Code 800  
Local Phone Number 555-5455  
Title of 12(b) Security Common Stock, par value $0.01 per share  
Trading Symbol FNB  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   359,143,514
Amendment Flag false  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Entity Central Index Key 0000037808  
Current Fiscal Year End Date --12-31