Nature of Business and Basis of Presentation - General (Details) MW in Thousands	Jun. 30, 2019 MW
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Generation capacity (in MW)	23

The generation capacity of the entity's power generation facilities as of the balance sheet date, expressed in megawatts.

No definition available.

Name:	nrg_PowerGenerationCapacityMegawatts
Namespace Prefix:	nrg_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	instant