Impairment of Long-Lived Assets (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Mar. 31, 2017	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Property, plant and equipment, net				$ 72,748		$ 71,555
Proceeds from Long-term Capital Lease Obligations			$ 360
Estimated residual value of leased assets			356
Proceeds From Lease Termination				0	$ 360
Impairment of Long-Lived Assets to be Disposed of				418
Gain (Loss) on Contract Termination			4
Impairment of long-lived assets and losses on regulatory assets				445	239
Wind Assets [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Property, plant and equipment, net			$ 60
Property, Plant, and Equipment, Fair Value Disclosure					24
Impairment of long-lived assets and losses on regulatory assets					$ 36
Constellation Energy Group LLC [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Tangible Asset Impairment Charges	$ 15	$ 119
Electricity Generation Plant, Non-Nuclear [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Impairment of Long-Lived Assets to be Disposed of				$ 418