Proposed Sale of Properties (Details) (Equitable Gas and Homeworks, USD $) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended	9 Months Ended
	Dec. 19, 2012	Sep. 30, 2013	Sep. 30, 2013
Equitable Gas and Homeworks
Equity in Nonconsolidated Investments
Percentage of ownership interests of Equitable Gas Company, LLC (Equitable Gas) and Equitable Homeworks, LLC (Homeworks) to PNG Companies	100.00%
Expenses related to the proposed sale of properties		$ 0.4	$ 3.3