XML 98 R119.htm IDEA: XBRL DOCUMENT v3.20.1
Benefit Plans and Other Postretirement Benefits - Fair Values of Pension Assets By Asset Category and Level Within the Fair Value Hierarchy (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Minimum      
Significant assumptions used to calculate NRG's benefit expense      
Aon Hewitt above median yield curve discount rate (in years) 6 months    
Maximum      
Significant assumptions used to calculate NRG's benefit expense      
Aon Hewitt above median yield curve discount rate (in years) 99 years    
Pension Benefits      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets $ 1,150 $ 981 $ 1,104
Significant assumptions used to calculate NRG's benefit obligations      
Discount rate 3.26% 4.38%  
Rate of compensation increase 3.00% 3.00%  
Significant assumptions used to calculate NRG's benefit expense      
Discount rate     4.26%
Expected return on plan assets 6.35% 6.17% 6.85%
Rate of compensation increase 3.00% 3.00% 3.00%
Pension Benefits | Minimum      
Significant assumptions used to calculate NRG's benefit expense      
Discount rate 4.38% 3.71%  
Pension Benefits | Maximum      
Significant assumptions used to calculate NRG's benefit expense      
Discount rate 4.20% 4.04%  
Pension Benefits | Common/collective trust investment — U.S. equity      
Target allocations      
Target allocation of pension plan assets (as percent) 20.00%    
Pension Benefits | Common/collective trust investment — non-U.S. equity      
Target allocations      
Target allocation of pension plan assets (as percent) 13.00%    
Pension Benefits | Common/collective trust investment — non-core assets      
Target allocations      
Target allocation of pension plan assets (as percent) 17.00%    
Pension Benefits | Common/collective trust investment — fixed income      
Target allocations      
Target allocation of pension plan assets (as percent) 50.00%    
Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1)      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets $ 12 $ 12  
Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Common/collective trust investment — U.S. equity      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 0 0  
Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Common/collective trust investment — non-U.S. equity      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 0 0  
Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Common/collective trust investment — non-core assets      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 0 0  
Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Common/collective trust investment — fixed income      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 0 0  
Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investment fund      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 12 12  
Pension Benefits | Significant Observable Inputs (Level 2)      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 721 609  
Pension Benefits | Significant Observable Inputs (Level 2) | Common/collective trust investment — U.S. equity      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 233 183  
Pension Benefits | Significant Observable Inputs (Level 2) | Common/collective trust investment — non-U.S. equity      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 73 53  
Pension Benefits | Significant Observable Inputs (Level 2) | Common/collective trust investment — non-core assets      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 143 117  
Pension Benefits | Significant Observable Inputs (Level 2) | Common/collective trust investment — fixed income      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 272 256  
Pension Benefits | Significant Observable Inputs (Level 2) | Short-term investment fund      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 0 0  
Pension Benefits | Total      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 733 621  
Pension Benefits | Total | Common/collective trust investment — U.S. equity      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 233 183  
Pension Benefits | Total | Common/collective trust investment — non-U.S. equity      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 73 53  
Pension Benefits | Total | Common/collective trust investment — non-core assets      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 143 117  
Pension Benefits | Total | Common/collective trust investment — fixed income      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 272 256  
Pension Benefits | Total | Short-term investment fund      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 12 12  
Pension Benefits | Fair Value Measured at Net Asset Value Per Share      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 1,150 981  
Pension Benefits | Fair Value Measured at Net Asset Value Per Share | Common/collective trust investment — non-U.S. equity      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 84 70  
Pension Benefits | Fair Value Measured at Net Asset Value Per Share | Common/collective trust investment — non-core assets      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 24 16  
Pension Benefits | Fair Value Measured at Net Asset Value Per Share | Common/collective trust investment — fixed income      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 279 249  
Pension Benefits | Fair Value Measured at Net Asset Value Per Share | Partnerships/joint ventures      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets 30 25  
Other Postretirement Benefits Plan      
Benefit Plans and Other Postretirement Benefits      
Fair value of plan assets $ 0 $ 0 $ 0
Significant assumptions used to calculate NRG's benefit obligations      
Discount rate 3.26% 4.37%  
Rate of compensation increase 0.00% 0.00%  
Significant assumptions used to calculate NRG's benefit expense      
Discount rate     4.29%
Expected return on plan assets 0.00% 0.00% 0.00%
Rate of compensation increase 0.00% 0.00% 0.00%
Other Postretirement Benefits Plan | Minimum      
Significant assumptions used to calculate NRG's benefit expense      
Discount rate 4.37% 3.71%  
Other Postretirement Benefits Plan | Maximum      
Significant assumptions used to calculate NRG's benefit expense      
Discount rate 4.08%  
Other Postretirement Benefits Plan | Postretirement Benefit Obligation      
Significant assumptions used to calculate NRG's benefit obligations      
Year Health care cost trend rate reaches ultimate trend rate 2028 2025  
Other Postretirement Benefits Plan | Postretirement Benefit Obligation | Before age 65      
Significant assumptions used to calculate NRG's benefit obligations      
Health care trend rate 7.50% 7.80% 7.00%
Other Postretirement Benefits Plan | Postretirement Benefit Obligation | Age 65 and after      
Significant assumptions used to calculate NRG's benefit obligations      
Health care trend rate 4.50% 4.50%  
Other Postretirement Benefits Plan | Net Period Benefit Cost/Credit      
Significant assumptions used to calculate NRG's benefit obligations      
Year Health care cost trend rate reaches ultimate trend rate 2025 2025 2025
Other Postretirement Benefits Plan | Net Period Benefit Cost/Credit | Before age 65      
Significant assumptions used to calculate NRG's benefit obligations      
Health care trend rate 7.80% 8.20%  
Other Postretirement Benefits Plan | Net Period Benefit Cost/Credit | Age 65 and after      
Significant assumptions used to calculate NRG's benefit obligations      
Health care trend rate 4.50% 4.50% 5.00%