Acquisitions (Details) (USD $)	12 Months Ended		12 Months Ended
	Dec. 31, 2011 Peak	Jul. 31, 2011 Peak	Dec. 31, 2011 Superior	Dec. 31, 2010 Superior	Sep. 30, 2010 Superior	Dec. 31, 2010 Energy Contractors
Preliminary Estimates for Allocation of Purchase Price as of Acquisition Date
Consideration paid in cash		$ 65,000,000			$ 681,300,000	$ 53,400,000
Equity interest acquired (as a percent)		50.00%
Previously held equity interest (as a percent)		50.00%
Previously held equity interest carrying value		38,100,000
Excess of the estimated value of the assets and liabilities over the net carrying value of previously held equity interest	13,100,000
Acquired price per common share					$ 22.12
Superior contributed revenues			1,200,000,000
Acquisition-related transaction costs				7,000,000
Assets:
Cash and cash equivalents					1,045,000
Accounts receivable					143,842,000
Inventory					33,963,000
Other current assets					7,612,000
Property, plant and equipment					415,000,000
Intangible assets					131,811,000
Goodwill	8,000,000				334,992,000	4,200,000
Other long-term assets					14,726,000
Total assets					1,082,991,000
Liabilities:
Current liabilities					78,277,000
Deferred income taxes					119,201,000
Long-term debt					124,792,000
Other long-term liabilities					10,258,000
Total liabilities					332,528,000
Preferred stock					69,188,000
Net assets acquired					$ 681,275,000