Commitments and Contingencies, Leases - Right-of-Use Assets (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Operating Right-of-Use Assets
Gross operating lease ROU assets	$ 1,843
Accumulated amortization	(80)
Net operating lease ROU assets	1,763	$ 0
Finance Right-of-Use Assets
Gross finance lease ROU assets	222
Accumulated amortization	(80)
Net finance lease ROU assets	142
PPAs
Operating Right-of-Use Assets
Gross operating lease ROU assets	1,642
Other
Operating Right-of-Use Assets
Gross operating lease ROU assets	201
Gas storage facilities
Finance Right-of-Use Assets
Gross finance lease ROU assets	201
Gas pipeline
Finance Right-of-Use Assets
Gross finance lease ROU assets	$ 21