Net Carrying Amount of Debt (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
Long term debt	$ 1,223,707		$ 911,718
Senior Secured Notes
Debt Instrument [Line Items]
Long term debt	600,000		600,000
1.50% Convertible Notes
Debt Instrument [Line Items]
Long term debt	311,538	[1]
2.50% Convertible Notes
Debt Instrument [Line Items]
Long term debt	257,669	[2]	254,718
Ecko Note
Debt Instrument [Line Items]
Long term debt	$ 54,500		$ 57,000

[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.

[2] Reflects the net debt carrying amount of the 2.50% 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 2.50% Convertible Notes is $300.0 million.