Inventory and Other Current Assets (Details) (USD $) Share data in Millions, unless otherwise specified	0 Months Ended	12 Months Ended
	Apr. 17, 2012	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Number of platforms to decommission		seven
Long term contract amount		$ 750,000,000
Costs and estimated earnings in excess of billings included in other current assets		18,500,000		133,400,000
Supplies and consumables		61,800,000	61,800,000	36,400,000
Raw materials		5,000,000		5,400,000
Work-in-progress		6,000,000		2,300,000
Finished goods		63,700,000		39,000,000
Inventory		136,500,000		83,100,000
Equity Method Investment, Net Sales Proceeds	34,100,000
Available-for-sale Equity Securities, Amortized Cost Basis	51,600,000
Number of shares comprising Available for Sale Securities	7.0	1.4
Available-for-Sale Securities, Share Price	7.33
Percentage of limited partnership interest	10.00%	10.00%
Available-for-sale securities, number of shares sold		5.6
Available-for-sale Securities, Income Tax Expense on Change in Unrealized Holding Gain (Loss)		500,000
Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss), Net of Tax		900,000
Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss) before Taxes		1,400,000
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds		41,900,000
Available-for-sale Securities, Gross Realized Gains		900,000
Available-for-sale Securities, Current		9,200,000
Wild Well [Member]
Costs and estimated earnings in excess of billings included in other current assets				$ 129,700,000