Accrued Liabilities and Deferred Credits (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Accounts Payable and Accrued Liabilities [Line Items]
Accrued compensation	$ 2,540	$ 1,687
Restructuring liability	227	790
Environmental and insurance liabilities	1,856	1,887
Deferred revenue	30,346	29,859
Retiree medical and other benefit reserves	89	100
Legal	1,572	2,972
Other accrued liabilities	13,774	10,196
Total accrued liabilities and deferred credits	$ 50,404	$ 47,491