Details of 2.50% Convertible Notes Reflected on Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Debt Instrument [Line Items]
Net debt carrying amount	$ 633,389		$ 584,387
2.50% Convertible Notes
Debt Instrument [Line Items]
Equity component carrying amount	35,996
Unamortized discount	56,836
Net debt carrying amount	$ 243,164	[1]

[1] Reflects the net debt carrying amount of the 2.50% Convertible Notes in the consolidated balance sheet as of December 31, 2011, in accordance with accounting for convertible notes. The principal amount owed to the holders of the Convertible Notes is $300.0 million.