Details of 2.50% Convertible Notes Reflected on Condensed Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Debt Instrument [Line Items]
Net debt carrying amount	$ 475,519		$ 633,389
2.50% Convertible Notes
Debt Instrument [Line Items]
Equity component carrying amount	35,996		35,996
Unamortized discount	48,285		56,836
Net debt carrying amount	$ 251,715	[1]	$ 243,164

[1] Reflects the net debt carrying amount of the 2.50% Convertible Notes in the consolidated balance sheet as of September 30, 2012, in accordance with accounting for convertible notes. The principal amount owed to the holders of the 2.50% Convertible Notes is $300.0 million.