Earnings (Loss) Per Share for Talen Energy Corporation (Details) - USD ($) $ in Millions		3 Months Ended		4 Months Ended	5 Months Ended		9 Months Ended
	Jun. 01, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	May. 31, 2015	[1]	Sep. 30, 2015		Sep. 30, 2014
Income (Numerator)
Income (Loss) from continuing operations after income taxes		$ (339)	$ 94				$ (218)		$ 38
Income (Loss) from discontinued operations (net of income taxes)		(62)	7				(61)		10
Net Income (Loss)		$ (401)	$ 101	$ (311)	$ 32		$ (279)		$ 48
Shares of Common Stock (Denominator)
Weighted-average shares - Basic EPS (in shares)		128,509,000	83,524,000				103,627,000		83,524,000
Weighted-average shares - Diluted EPS (in shares)		128,509,000	83,524,000				103,627,000		83,524,000
Shares Issued (Numeric) [Abstract]
Antidilutive securities excluded from computation of earnings per share (in shares)		1,263,000					525,000
Common Stock
Schedule of Capitalization, Equity [Line Items]
Stock issuance (shares)	128,499,023
Common stock shares issued to PPL shareholders	83,524,365						83,524,000	[2]
Common stock issued for acquisition of RJS Power, shares	44,974,658						44,975,000	[2]

[1] Represents Talen Energy Supply's predecessor member's equity balance and activity prior to the June 1, 2015 spinoff transaction.

[2] Shares in thousands. Each share entitles the holder to one vote on any questions presented at any stockholders' meeting.