Details of Two Point Five Zero Percent Convertible Notes Reflected on Condensed Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
Net debt carrying amount	$ 1,440,630		$ 911,718
2.50% Convertible Notes
Debt Instrument [Line Items]
Equity component carrying amount	35,996		35,996
Unamortized discount	39,380		45,282
Net debt carrying amount	$ 260,620	[1]	$ 254,718

[1] Reflects the net debt carrying amount of the 2.50% Convertible Notes in the consolidated balance sheet as of June 30, 2013, in accordance with accounting for convertible notes. The principal amount owed to the holders of the 2.50% Convertible Notes is $300.0 million.