Environmental Matters (GenOn, GenOn Americas Generation and GenOn Mid-Atlantic) (Details)		1 Months Ended
	Jul. 28, 2015 state	Apr. 30, 2017 petition
Site Contingency [Line Items]
Number of petitions granted by EPA to reconsider the rule | petition		2
Sulfur Dioxide Budgets
Site Contingency [Line Items]
Number of states required to revise budgets	4
Nitrogen Oxides Budget
Site Contingency [Line Items]
Number of states required to revise budgets	11