v3.26.3
COVER - shares
9 Months Ended
Sep. 30, 2026
Oct. 31, 2026
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2026  
Document Transition Report false  
Entity File Number 001-16581  
Entity Registrant Name SANTANDER HOLDINGS USA, INC.  
Entity Incorporation, State or Country Code VA  
Entity Tax Identification Number 23-2453088  
Entity Address, Address Line One 75 State Street  
Entity Address, City or Town Boston  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 02109  
City Area Code 800  
Local Phone Number 493-8219  
Title of 12(b) Security Depositary Shares, Each Representing a 1/1,000thInterest in a Share of Fixed-Rate Reset Non-Cumulative Perpetual Preferred Stock, Series H  
Trading Symbol SNUS PF H  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Emerging Growth Company false  
Entity Filer Category Non-accelerated Filer  
Entity Small Business false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   530,391,043
Entity Central Index Key 0000811830  
Amendment Flag false  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q3  
Current Fiscal Year End Date --12-31