Earnings Per Share - Additional Information (Detail) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 14, 2019	Dec. 31, 2018	Sep. 30, 2018	Feb. 22, 2018
Earnings Per Share Disclosure [Line Items]
Anti-dilutive shares	300,000	600,000
Debt instrument, interest rate, stated percentage	5.75%
5.75% Senior Subordinated Notes Due August 2023
Earnings Per Share Disclosure [Line Items]
Debt instrument, interest rate, stated percentage	5.75%	5.75%	5.75%
Convertible Notes
Earnings Per Share Disclosure [Line Items]
Debt instrument, interest rate, stated percentage					1.50%
Convertible Notes | 5.75% Senior Subordinated Notes Due August 2023
Earnings Per Share Disclosure [Line Items]
Debt instrument, interest rate, stated percentage	5.75%	5.75%		5.75%		5.75%
Performance Shares
Earnings Per Share Disclosure [Line Items]
Anti-dilutive shares	0	800,000