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v3.21.2

Changes in Capital Structure - Changes in NRG's common stock issued and outstanding (Details) - shares | 1 Months Ended | 9 Months Ended
--- | --- | ---
Nov. 04, 2021 | Sep. 30, 2021
Schedule of Stock by Class, Equity [Roll Forward] |  |
Balance as of beginning of period (in shares) | 423,545,261 | 423,057,848
Treasury shares, balance as of beginning of period (in shares) | (178,765,948) | (178,825,915)
Outstanding, as of beginning of period (in shares) | 244,779,313 | 244,231,933
Balance as of end of period (in shares) |  | 423,545,261
Treasury shares, balance as of end of the period (in shares) |  | (178,765,948)
Outstanding, as of end of period (in shares) |  | 244,779,313
Shares issued under LTIPs |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Shares issued under LTIPs (in shares) |  | 487,413
Shares issued under ESPP |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Stock issued under ESPP (in shares) |  | 59,967
Subsequent Event |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Outstanding, as of end of period (in shares) | 244,838,651 |
Subsequent Event | Shares issued under LTIPs |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Shares issued under LTIPs (in shares) | 1,913 |
Subsequent Event | Shares issued under ESPP |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Stock issued under ESPP (in shares) | 57,425 |
Common Stock |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Balance as of beginning of period (in shares) | 423,545,261 | 423,057,848
Balance as of end of period (in shares) |  | 423,545,261
Common Stock | Shares issued under LTIPs |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Shares issued under LTIPs (in shares) |  | 487,413
Common Stock | Shares issued under ESPP |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Stock issued under ESPP (in shares) |  | 0
Common Stock | Subsequent Event |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Balance as of end of period (in shares) | 423,547,174 |
Common Stock | Subsequent Event | Shares issued under LTIPs |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Shares issued under LTIPs (in shares) | 1,913 |
Common Stock | Subsequent Event | Shares issued under ESPP |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Stock issued under ESPP (in shares) | 0 |
Treasury |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Treasury shares, balance as of beginning of period (in shares) | (178,765,948) | (178,825,915)
Treasury shares, balance as of end of the period (in shares) |  | (178,765,948)
Treasury | Shares issued under LTIPs |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Shares issued under LTIPs (in shares) |  | 0
Treasury | Shares issued under ESPP |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Stock issued under ESPP (in shares) |  | 59,967
Treasury | Subsequent Event |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Treasury shares, balance as of end of the period (in shares) | (178,708,523) |
Treasury | Subsequent Event | Shares issued under LTIPs |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Shares issued under LTIPs (in shares) | 0 |
Treasury | Subsequent Event | Shares issued under ESPP |  |
Schedule of Stock by Class, Equity [Roll Forward] |  |
Stock issued under ESPP (in shares) | 57,425 |

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- Definition Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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