Details of Two Point Five Zero Percent Convertible Notes Reflected on Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Sep. 30, 2015		Dec. 31, 2014
Debt Instrument [Line Items]
Long-term debt, including current portion, Carrying Amount	$ 1,471,642		$ 1,394,077
Convertible Notes | 2.50% Senior Subordinated Notes Due June 2016
Debt Instrument [Line Items]
Equity component carrying amount	35,996		35,996
Unamortized discount	9,579		19,896
Long-term debt, including current portion, Carrying Amount	$ 290,421	[1]	$ 280,104

[1] Reflects the net debt carrying amount of the 2.50% Convertible Notes in the consolidated balance sheet as of September 30, 2015, in accordance with accounting for convertible notes. The principal amount owed to the holders of the 2.50% Convertible Notes is $300.0 million.