Company's Debt Maturities on Calendar Year Basis (Parenthetical) (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Mar. 14, 2019	Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2018	Feb. 22, 2018	Oct. 27, 2017	Oct. 26, 2017	Aug. 02, 2017	Nov. 29, 2012
Debt Instrument [Line Items]
Principal amount of long term debt							$ 240.7
Debt instrument, interest rate, stated percentage	5.75%
5.75% Senior Subordinated Notes Due August 2023
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	5.75%	5.75%			5.75%
Variable Funding Notes
Debt Instrument [Line Items]
Principal amount of long term debt	$ 100.0									$ 100.0
Senior Secured Term Loan
Debt Instrument [Line Items]
Principal amount of long term debt	188.5						$ 57.8	$ 300.0	$ 300.0
Convertible Notes
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage				1.50%
Convertible Notes | 5.75% Senior Subordinated Notes Due August 2023
Debt Instrument [Line Items]
Principal amount of long term debt	$ 105.7		$ 109.7			$ 125.0
Debt instrument, interest rate, stated percentage	5.75%		5.75%		5.75%	5.75%