Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified			3 Months Ended	6 Months Ended			12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Dec. 31, 2007 ACP [Member]	Jun. 30, 2012 ACP [Member]	Jun. 30, 2012 SB Decking [Member]	Jun. 30, 2012 VAT, Total [Member]	Dec. 31, 2010 VAT, Total [Member]	Dec. 31, 2010 VAT Settlement One [Member]	Dec. 31, 2010 VAT Settlement Two [Member]
Loss Contingencies [Line Items]
Gain (Loss) Related to Litigation Settlement			$ 2,000				$ 4,132	$ 3,901	$ 231
Loss Contingency, Range of Possible Loss, Minimum				1,100		0
Loss Contingency, Range of Possible Loss, Maximum				2,100		16,500
P-2 well operation range estimate				one and one-half to four and one-half years
P-3 well operation range estimate				one and one-half to four and one-half years
Unrelated Environmental Liability Accruals	255	493
Loss Contingency, Estimate of Possible Loss					$ 4,900
Loss Contingency, Settlement Agreement, Terms					In response, two of the three carriers entered into separate settlement and release agreements with the subsidiary in late 2005 and in the first quarter of 2007 for $15,000 and $20,000, respectively. The payments under the latest settlement and release agreement were structured to be received over a four-year period with annual installments of $5,000, the final installment of which was received in the first quarter of 2010. The proceeds of both settlements are restricted and can only be used to pay claims and costs of defense associated with the subsidiary’s asbestos litigation. During the third quarter of 2007, the subsidiary and the remaining primary insurance carrier entered into a Claim Handling and Funding Agreement, under which the carrier will pay 27% of defense and indemnity costs incurred by or on behalf of the subsidiary in connection with asbestos bodily injury claims for a minimum of five years beginning July 1, 2007. The agreement continues until terminated and can only be terminated by either party by providing the other party with a minimum of two years prior written notice. At the end of the term of the agreement, the subsidiary may choose to again pursue its claim against this insurer regarding the application of the policy limits.
Percentage of potential exposure represented by one jurisdiction						82.00%