Effective Annual Interest Rates on Senior Subordinated Convertible Notes (Detail)	Dec. 31, 2015
Convertible Notes Due Two Thousand Eighteen
Debt Instrument [Line Items]
Effective interest rate	5.50%
Convertible Notes Due Two Thousand Nineteen
Debt Instrument [Line Items]
Effective interest rate	5.60%
Convertible Notes Due Two Thousand Thirty Four
Debt Instrument [Line Items]
Effective interest rate	5.50%