Commitments and Contingencies (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Pending or Threatened Litigation [Member] Litigation related to construction materials [Member]	Aug. 31, 2011 Pending or Threatened Litigation [Member] Litigation related to construction materials [Member]	Jan. 18, 2011 Pending or Threatened Litigation [Member] Litigation related to construction materials [Member]	Dec. 31, 2011 Pending or Threatened Litigation [Member] Natural gas gathering operations [Member]	Apr. 20, 2011 Pending or Threatened Litigation [Member] Natural gas gathering operations [Member]	Oct. 31, 2010 Pending or Threatened Litigation [Member] Natural gas gathering operations [Member]	Sep. 30, 2010 Pending or Threatened Litigation [Member] Natural gas gathering operations [Member]	Jan. 13, 2012 Pending or Threatened Litigation [Member] Guarantee obligation under construction contract [Member]	Sep. 19, 2011 Pending or Threatened Litigation [Member] Guarantee obligation under construction contract [Member]	Dec. 31, 2009 Pending or Threatened Litigation [Member] Guarantee obligation under construction contract [Member]	Jul. 31, 2007 Pending or Threatened Litigation [Member] Guarantee obligation under construction contract [Member]
Loss Contingencies [Line Items]
Potential liabilities related to litigation and environmental matters	$ 64,100,000	$ 45,300,000						$ 26,600,000
Bicent's bank letter of credit guaranteeing CEM's obligation													10,000,000
Amount of compensatory damages in LPP's notice of demand												149,700,000
Estimated damages in pending litigation, low estimate					6,000,000	18,800,000
Estimated damages in pending litigation, high estimate					11,000,000	22,600,000
Amount Of Damages Dismissed In Pending Litigation			5,000,000
Estimated Damages Including Interest In Amended Complaint			21,900,000
Loss Contingency, Estimate of Possible Loss				3,700,000
Additional Amount Per Day of Potential Penalties				5,000
Amount of natural gas gathering contract dispute charged to operation and maintenance expense, after tax									16,500,000
Amount of natural gas gathering contract dispute charged to operations and maintenance, before tax									26,600,000
Amount Of Counterclaim											14,000,000
Arbitration Award										22,000,000
Legal Fees And Expenses Awarded In Litigation							$ 293,000