Summary of Significant Accounting Policies (GenOn, GenOn Americas Generation and GenOn Mid-Atlantic) (Tables)

9 Months Ended

Sep. 30, 2017

Accounting Policies [Abstract]

Schedule of accumulated depreciation and accumulated amortization

The following table presents the accumulated depreciation included in property, plant and equipment, net, and accumulated amortization included in intangible assets, net, respectively, for each of the Registrants as of September 30, 2017 and December 31, 2016:

	Property, plant and equipment Accumulated depreciation				Intangible assets Accumulated amortization
	September 30, 2017		December 31, 2016		September 30, 2017		December 31, 2016
	(In millions)
GenOn	$	730	$	604	$	66	$	87
GenOn Americas Generation	329		275		66		87
GenOn Mid-Atlantic	284		237		33		29