SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Summary of Significant Accounting Policies - Inventory (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012 Successor MMbtu		Dec. 31, 2011 Predecessor MMbtu
Natural Gas Volumes	34,891,000		29,718,000
Natural Gas Inventory	$ 124	[1]	$ 96	[1]
Inventory, Raw Materials and Supplies	20		19
System natural gas and operating supplies	144		115
Inventory, Gas in Storage Underground, Noncurrent	0	[1]	3	[1]
Energy Related Inventory	$ 144		$ 118

[1] Natural gas volumes held for operations at December 31, 2012 and 2011 were 34,891,000 MMBtu and 29,718,000 MMBtu, respectively.