Impairment of Long-Lived Assets (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Property, plant and equipment, net	$ 73,067				$ 73,067		$ 71,555
Proceeds from Long-term Capital Lease Obligations			$ 360
Capital Leases, Net Investment in Direct Financing Leases, Unguaranteed Residual Values of Leased Property			356
Gain (Loss) on Contract Termination		$ 36	4
Impairment of long-lived assets and losses on regulatory assets					488	$ 274
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
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	$ 40