ESTIMATES, SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND BALANCE SHEET DETAIL Estimates, Significant Accounting Policies and Balance Sheet Detail - Inventory (Details) MMbtu in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2020 USD ($) MMbtu	Dec. 31, 2019 USD ($) MMbtu	Dec. 31, 2018 USD ($)
Inventory Accounting Policies [Abstract]
Energy Related Inventory, Natural Gas in Storage	[1]	$ 63	$ 39
Inventory, Raw Materials and Supplies		23	22
Inventories		$ 86	$ 61
Natural Gas Volumes | MMbtu		29.2	19.3
Interest Costs Capitalized		$ 0	$ 2	$ 1

[1] Natural gas volumes held for operations at December 31, 2020 and 2019 were 29.2 TBtu and 19.3 TBtu, respectively.