Changes in Capital Structure - Changes in NRG's Common Stock Issued and Outstanding (Details) - shares	1 Months Ended	6 Months Ended
	Jul. 31, 2024	Jun. 30, 2024
Schedule of Stock by Class, Equity [Roll Forward]
Preferred, Balance as of beginning of period (in shares)	650,000	650,000
Preferred, Balance as of end of period (in shares)		650,000
Common, Balance as of beginning of period (in shares)	266,552,386	267,330,470
Treasury, Balance as of beginning of period (in shares)	(59,053,958)	(59,199,520)
Common, Outstanding, as of beginning of period (in shares)	207,498,428	208,130,950
Shares repurchased (in shares)		(2,277,630)
Common, Balance as of end of period (in shares)		266,552,386
Treasury, Balance as of end of period (in shares)		(59,053,958)
Common, Outstanding, as of end of period (in shares)		207,498,428
Subsequent Event
Schedule of Stock by Class, Equity [Roll Forward]
Shares repurchased (in shares)	(1,127,232)
Partial settlement of Capped Call Options (in shares)	(1,067)
Common, Outstanding, as of end of period (in shares)	206,379,832
Shares issued under LTIPs
Schedule of Stock by Class, Equity [Roll Forward]
Shares issued under LTIPs (in shares)		1,499,546
Shares issued under LTIPs | Subsequent Event
Schedule of Stock by Class, Equity [Roll Forward]
Shares issued under LTIPs (in shares)	9,703
Shares issued under ESPP
Schedule of Stock by Class, Equity [Roll Forward]
Shares issued under ESPP (in shares)		145,562
Preferred Stock
Schedule of Stock by Class, Equity [Roll Forward]
Preferred, Balance as of beginning of period (in shares)	650,000
Preferred, Balance as of end of period (in shares)		650,000
Preferred Stock | Subsequent Event
Schedule of Stock by Class, Equity [Roll Forward]
Preferred, Balance as of end of period (in shares)	650,000
Common Stock
Schedule of Stock by Class, Equity [Roll Forward]
Common, Balance as of beginning of period (in shares)	266,552,386	267,330,470
Retirement of treasury stock (in shares)		(2,277,630)
Common, Balance as of end of period (in shares)		266,552,386
Common Stock | Subsequent Event
Schedule of Stock by Class, Equity [Roll Forward]
Retirement of treasury stock (in shares)	(955,232)
Common, Balance as of end of period (in shares)	265,606,857
Common Stock | Shares issued under LTIPs
Schedule of Stock by Class, Equity [Roll Forward]
Shares issued under LTIPs (in shares)		1,499,546
Common Stock | Shares issued under LTIPs | Subsequent Event
Schedule of Stock by Class, Equity [Roll Forward]
Shares issued under LTIPs (in shares)	9,703
Treasury Stock
Schedule of Stock by Class, Equity [Roll Forward]
Treasury, Balance as of beginning of period (in shares)	(59,053,958)	(59,199,520)
Shares repurchased (in shares)		(2,277,630)
Retirement of treasury stock (in shares)		2,277,630
Treasury, Balance as of end of period (in shares)		(59,053,958)
Treasury Stock | Subsequent Event
Schedule of Stock by Class, Equity [Roll Forward]
Shares repurchased (in shares)	(1,127,232)
Partial settlement of Capped Call Options (in shares)	(1,067)
Retirement of treasury stock (in shares)	955,232
Treasury, Balance as of end of period (in shares)	(59,227,025)
Treasury Stock | Shares issued under LTIPs | Subsequent Event
Schedule of Stock by Class, Equity [Roll Forward]
Shares issued under LTIPs (in shares)	0
Treasury Stock | Shares issued under ESPP
Schedule of Stock by Class, Equity [Roll Forward]
Shares issued under ESPP (in shares)		145,562