Commitment and Contingenices (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Refundable Gas Costs		$ 11,000,000
Contingent Residual Support Agreement, Amount	$ 2,000,000,000
Estimated litigation liability	22,000,000		$ 21,000,000
Regency 4.50% Senior Notes Due 2023 [Member]
Loss Contingencies [Line Items]
Guarantor Obligations, Current Carrying Value	$ 600,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.50%
Attorney General of Commonwealth [Member]
Loss Contingencies [Line Items]
Legal Fees	$ 19,000,000
Percentage Of Recovery	50.00%
Reimbursement expert and consultant cost, maximum	$ 150,000