Accrued Liabilities and Deferred Credits (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Accounts Payable and Accrued Liabilities [Line Items]
Accrued compensation	$ 3,508	$ 1,687
Restructuring liability	202	790
Environmental and insurance liabilities	1,859	1,887
Deferred revenue	27,222	29,859
Legal	1,025	2,972
Other accrued liabilities	13,980	10,296
Total accrued liabilities and deferred credits	$ 47,796	$ 47,491