Long-Term Debt (Convertible Debt) - Additional Information (Detail)			6 Months Ended	9 Months Ended
	Aug. 05, 2016 USD ($) $ / shares	Mar. 11, 2015 USD ($) $ / shares	Jun. 30, 2016 USD ($) $ / shares	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Debt Instrument [Line Items]
Amount of loan issued			$ 141,300,000	$ 141,300,000
Debt instrument conversion ratio	14.5195
Convertible notes principal amount	$ 1,000
Conversion price per share | $ / shares	$ 68.87	$ 68.90
Unamortized debt discount of notes				$ 4,406,375
4.50% Convertible Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Amount of loan issued		$ 75,000,000			$ 75,000,000
Debt Instrument Maturity Year			2020	2020	2020
Debt instrument interest rate		4.50%	4.50%	4.50%
Line of credit facility, maturity date		Mar. 15, 2020
Debt instrument conversion ratio		14.5136
Convertible notes principal amount		$ 1,000
Conversion price per share | $ / shares	$ 68.87		$ 68.90
Unamortized debt discount of notes		6,100,000		$ 4,400,000
Cash Discount for issuance of the notes		2,600,000
Equity component of the convertible notes issued		3,500,000			$ 2,100,000
Net proceeds from issuance of notes		72,400,000
Credit facility repayments		$ 47,500,000