Company's Debt Maturities on Calendar Year Basis (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Mar. 14, 2019	Dec. 31, 2018	Sep. 30, 2018	Feb. 22, 2018	Oct. 27, 2017	Oct. 26, 2017	Sep. 30, 2017	Aug. 02, 2017	Nov. 29, 2012
Debt Instrument [Line Items]
Principal amount of long term debt						$ 240.7
Percentage of conversion of convertible notes				5.75%
5.75% Senior Subordinated Notes Due August 2023
Debt Instrument [Line Items]
Percentage of conversion of convertible notes	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	182.7					$ 57.8	$ 300.0		$ 300.0
Convertible Notes
Debt Instrument [Line Items]
Percentage of conversion of convertible notes								1.50%
Convertible Notes | 5.75% Senior Subordinated Notes Due August 2023
Debt Instrument [Line Items]
Principal amount of long term debt	$ 94.4		$ 109.7		$ 125.0
Percentage of conversion of convertible notes	5.75%		5.75%	5.75%	5.75%