Financing Arrangements (Convertible Senior Notes) - Additional Information (Detail)	3 Months Ended	6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) $ / shares shares	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2012 USD ($)
Debt Disclosure [Abstract]
Convertible senior notes		$ 0	$ 0		$ 0	$ 112,500,000
Convertible senior notes interest rate						3.75%
Convertible senior notes convertible latest date		Aug. 15, 2019
Initial conversion rate, number of common stock issuable			0.1333
Debt conversion, maximum number of common stock shares | shares		15,000,000
Conversion price per share | $ / shares		$ 7.50			$ 7.50
Convertible senior notes, transactional fees			$ 0			$ 3,537,000
Amount of shares issued upon conversion | shares		15,000,000
Amount of discount on convertible notes					$ 108,955,000
Convertible senior notes, unamortized discount		$ 3,395,000			$ 3,395,000
Convertible senior notes, total interest and amortization expense recognized	$ 767,000			$ 3,273,000