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		Dec. 31, 2018 USD ($) MMbtu	Dec. 31, 2017 USD ($) MMbtu
Inventory Accounting Policies [Abstract]
Energy Related Inventory, Natural Gas in Storage	[1]	$ 79	$ 132
Natural Gas Volumes | MMbtu		25.9	37.9
Inventory, Raw Materials and Supplies		$ 19	$ 18
Inventories		$ 98	$ 150

[1] Natural gas volumes held for operations at December 31, 2018 and 2017 were 25.9 TBtu and 37.9 TBtu, respectively.