v3.19.3
Cover - shares
9 Months Ended
Sep. 30, 2019
Oct. 31, 2019
Cover page.    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2019  
Document Transition Report false  
Entity File Number 001-15891  
Entity Registrant Name NRG Energy, Inc  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 41-1724239  
Entity Address, Address Line One 804 Carnegie Center,  
Entity Address, City or Town Princeton  
Entity Address, State or Province NJ  
Entity Address, Postal Zip Code 08540  
City Area Code 609  
Local Phone Number 524-4500  
Title of 12(b) Security Common Stock, par value $0.01  
Trading Symbol NRG  
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   251,594,290
Entity Central Index Key 0001013871  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3