Sales of Properties and Contracts (Details) (USD $)	12 Months Ended			0 Months Ended	12 Months Ended	1 Months Ended		12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 17, 2013 Equitable Gas and Homeworks	Dec. 31, 2013 Equitable Gas and Homeworks MMcf item	Feb. 28, 2011 Langley	Jul. 31, 2011 Big Sandy Pipeline	Dec. 31, 2012 Lycoming County, Pennsylvania acre	Dec. 31, 2011 Lycoming County, Pennsylvania acre	Dec. 31, 2013 Westmoreland County, Pennsylvania acre
Equity in Nonconsolidated Investments
Sale of energy marketing contracts					$ 20,000,000
Number of customers with whom natural gas sale agreements are entered					1,000
Sale volumes of energy marketing contracts (in Mcf)					12,000
Proceeds from sale of energy marketing contracts in cash	23,000,000				18,000,000
Amount expected to be collected					2,000,000
Gain on sale of energy marketing contracts					19,600,000
Pre-tax gain on sale of business						22,800,000	180,100,000	2,000,000	3,900,000	400,000
Number of customers with whom natural gas sale agreements are entered related to certain acquired assets					50
Value of energy marketing contracts				5,000,000
Sale of energy marketing contracts related to certain acquired assets					5,000,000
Net proceeds from sale of business				740,600,000			390,000,000			400,000
Size of land under sold leases (in acres)								2,900	2,900	128
Net proceeds after purchase price adjustments	$ 740,587,000	$ 4,842,000	$ 619,999,000			$ 230,000,000		$ 2,700,000	$ 6,000,000