Details of One Point Five Zero Percent Convertible Notes Reflected on Condensed Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
Net debt carrying amount	$ 1,223,707		$ 911,718
1.50% Convertible Notes
Debt Instrument [Line Items]
Equity component carrying amount	49,931
Unamortized discount	88,462
Net debt carrying amount	$ 311,538	[1]

[1] Reflects the net debt carrying amount of the 1.50% Convertible Notes in the consolidated balance sheet as of March 31, 2013, in accordance with accounting for convertible notes. The principal amount owed to the holders of the 1.50% Convertible Notes is $400.0 million.