Long-Term Debt - Schedule of Long-Term Debt (Parenthetical) (Detail) - 4.50% Convertible Senior Notes due 2020 [Member]	6 Months Ended	9 Months Ended
	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Mar. 11, 2015
Debt Instrument [Line Items]
Debt instrument interest rate	4.50%	4.50%		4.50%
Debt Instrument Maturity Year	2020	2020	2020