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Cover Cover
Nov. 04, 2021
Aug. 05, 2021
May 07, 2020
Cover [Abstract]      
Document Type 8-K    
Entity Registrant Name NRG ENERGY, INC.    
Document Period End Date Nov. 01, 2021    
Entity Central Index Key     0001013871
Amendment Flag     false
Entity Incorporation, State or Country Code   DE  
Entity File Number 001-15891    
Entity Tax Identification Number   41-1724239  
Entity Address, Address Line One 910 Louisiana Street    
Entity Address, City or Town Houston    
Entity Address, State or Province TX    
Entity Address, Postal Zip Code 77002    
City Area Code 713    
Local Phone Number 537-3000    
Written Communications false    
Soliciting Material false    
Pre-commencement Tender Offer false    
Pre-commencement Issuer Tender Offer false    
Title of 12(b) Security Common Stock, par value $0.01    
Trading Symbol NRG    
Security Exchange Name NYSE    
Entity Emerging Growth Company false