Details of Two Point Five Zero Percent Convertible Notes Reflected on Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Net debt carrying amount	$ 1,401,783		$ 1,427,319
2.50% Convertible Notes
Debt Instrument [Line Items]
Equity component carrying amount	35,996		35,996
Unamortized discount	23,300		32,987
Net debt carrying amount	$ 276,700	[1]	$ 267,013

[1] Reflects the net debt carrying amount of the 2.50% Convertible Notes in the consolidated balance sheet as of September 30, 2014, in accordance with accounting for convertible notes. The principal amount owed to the holders of the 2.50% Convertible Notes is $300.0 million.