Aggregate Contractual Maturities of Indebtedness by Year (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
7.0% convertible senior notes
Extinguishment Of Debt [Line Items]
Convertible senior notes interest rate	7.00%	7.00%
7.0% convertible senior notes | Recourse Indebtedness
Extinguishment Of Debt [Line Items]
Aggregate principal amount of notes issued		$ 871
Convertible senior notes interest rate	7.00%	7.00%
4.0% convertible senior notes
Extinguishment Of Debt [Line Items]
Convertible senior notes interest rate	4.00%	4.00%
4.0% convertible senior notes | Recourse Indebtedness
Extinguishment Of Debt [Line Items]
Aggregate principal amount of notes issued		$ 126,098
Convertible senior notes interest rate	4.00%	4.00%