SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Summary of Significant Accounting Policies - Inventory (Details) MMbtu in Millions, $ in Millions		Dec. 31, 2015 USD ($) MMbtu	Dec. 31, 2014 USD ($) MMbtu
Natural Gas Volumes | MMbtu		43.2	34.3
Natural Gas Inventory	[1]	$ 98	$ 105
Inventory, Raw Materials and Supplies		15	14
Inventories		113	119
Energy Related Inventory		$ 113	$ 119

[1] Natural gas volumes held for operations at December 31, 2015 and 2014 were 43.2 TBtu and 34.3 TBtu, respectively.