Indebtedness - Early Extinguishment of Debt - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Jan. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Subsequent Event
Debt Instrument [Line Items]
Interest rate on notes	9.25%
Repayment of notes by early cash tender premium amount	$ 15.1
Early cash tender offer period	10 days
5.75% Senior Notes Due 2021
Debt Instrument [Line Items]
Extinguishment of debt, principal amount		$ 101.8	$ 101.8
Interest rate on notes		5.75%	5.75%	5.75%
5.75% Senior Notes Due 2021 | Subsequent Event
Debt Instrument [Line Items]
Interest rate on notes	5.75%
5.875% Senior Notes Due 2022
Debt Instrument [Line Items]
Extinguishment of debt, principal amount		$ 31.6	$ 31.6
Interest rate on notes		5.875%	5.875%	5.875%
5.875% Senior Notes Due 2022 | Subsequent Event
Debt Instrument [Line Items]
Interest rate on notes	5.875%
5.00% Senior Notes Due 2022
Debt Instrument [Line Items]
Extinguishment of debt, principal amount		$ 68.1	$ 68.1
Interest rate on notes		5.00%	5.00%	5.00%
5.75% Senior Notes Due 2021 and 5.875% Senior Notes Due 2022 | Subsequent Event
Debt Instrument [Line Items]
Cash tender principal amount	$ 500.0