Net Carrying Amount of Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2015		Dec. 31, 2014
Debt Instrument [Line Items]
Long term debt	$ 1,471,642		$ 1,394,077
Senior Secured Notes
Debt Instrument [Line Items]
Long term debt	728,189		774,030
Convertible Notes | 1.50% Senior Subordinated Notes Due March 15, 2018
Debt Instrument [Line Items]
Long term debt	353,032	[1]	339,943
Convertible Notes | 2.50% Senior Subordinated Notes Due June 2016
Debt Instrument [Line Items]
Long term debt	290,421	[2]	$ 280,104
Variable Funding Notes
Debt Instrument [Line Items]
Long term debt	$ 100,000

[1] Reflects the net debt carrying amount of the 1.50% 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 1.50% Convertible Notes is $400.0 million.

[2] 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.