Liabilities for Dispositions and Discontinued Operations Analysis of Activity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance, beginning of period	$ 90,824	$ 93,160
Expenditures charged to liabilities	(1,711)	(9,209)
Increase to liabilities	12	6,873
Balance, end of period	89,125	90,824
Less: Current portion	(9,931)	(9,931)
Non-current portion	$ 79,194	$ 80,893