Business and Basis of Presentation (Details) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		5 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2015 USD ($) $ / shares	Jun. 30, 2014 USD ($) $ / shares	May. 31, 2015 USD ($)		Jun. 30, 2015 USD ($) asset_group $ / shares MW	Jun. 30, 2014 USD ($) $ / shares	Jun. 01, 2015 USD ($)	Dec. 31, 2014 USD ($)
Restructuring Cost and Reserve [Line Items]
TSA term of agreement						2 years
Goodwill	$ 470	$ 470		$ 72		$ 470			$ 72
Retail energy		243	$ 280			554	$ 630
Income from continuing operations after income taxes		25	2			121	(56)
Net income	90	$ 26	$ 13	$ 32	[1]	$ 122	$ (53)
Earnings per share (in dollars per share) | $ / shares		$ 0.26	$ 0.16			$ 1.34	$ (0.63)
Spinoff from PPL
Restructuring Cost and Reserve [Line Items]
Restructuring costs		$ 8				$ 10
Spinoff | Spinoff from PPL
Restructuring Cost and Reserve [Line Items]
Amount of accrued liability for separation benefits	2	2				$ 2			9
Number of asset groups that will be divested | asset_group						1
Number of asset groups proposed to be divested, one of which to be selected | asset_group						2
RJS Power
Restructuring Cost and Reserve [Line Items]
Goodwill								$ 398
Talen Energy Supply
Restructuring Cost and Reserve [Line Items]
Accelerated stock based compensation and pro-rated stock-based compensation awards		25				$ 25
Goodwill	$ 470	470				470			$ 72
Retail energy		243	$ 280			554	$ 630
Income from continuing operations after income taxes		25	2			121	(56)
Net income		26	$ 13			122	$ (53)
Restatement adjustment | Revenue Adjustment
Restructuring Cost and Reserve [Line Items]
Retail energy		(7)				(7)
Income from continuing operations after income taxes		(4)				(4)
Net income		$ (4)				$ (4)
Earnings per share (in dollars per share) | $ / shares		$ (0.04)				$ (0.04)
Minimum | Spinoff | Spinoff from PPL
Restructuring Cost and Reserve [Line Items]
Capacity, in total, to be divested in connection with the spinoff | MW						1,300
Maximum | Spinoff | Spinoff from PPL
Restructuring Cost and Reserve [Line Items]
Capacity, in total, to be divested in connection with the spinoff | MW						1,400

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