Commitments and Contingencies - Narrative (Details) (USD $)			3 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Regency 4.50% Senior Notes Due 2023 [Member]	Mar. 31, 2013 North Attleboro Site [Member]	Mar. 31, 2013 Attorney General of Commonwealth [Member]	Mar. 31, 2013 Mercury Release [Member]	Sep. 30, 2012 Mercury Release [Member]	Dec. 31, 2009 Mercury Release [Member]	Mar. 31, 2013 Accrued Liabilities [Member]	Dec. 31, 2012 Accrued Liabilities [Member]
Commitments And Contingencies [Line Items]
Guarantor Obligations, Current Carrying Value	$ 600,000,000
Debt Instrument, Interest Rate, Stated Percentage		4.50%
Estimated remediation costs to completion			11,000,000
Legal fees				19,000,000
Level of recovery				50.00%
Reimbursed expert and consultant costs, maximum				150,000
Estimated cost							6,000,000
Community Service Obligation							12,000,000
Original Fine Amount						50,000
Fine Amount Sought						500,000
Accrued liabilities, litigation and other claim-related					$ 500,000			$ 27,000,000	$ 27,000,000