Guarantor Subsidiaries - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018
Guarantor Subsidiaries [Line Items]
Percentage of Guarantor Subsidiaries	100.00%
7.625% Senior Notes [Member]
Guarantor Subsidiaries [Line Items]
Debt, stated interest rate	7.625%
7.0% Senior Notes [Member]
Guarantor Subsidiaries [Line Items]
Debt, stated interest rate	7.00%
Eight Point Seven Five Percentage Senior Notes [Member]
Guarantor Subsidiaries [Line Items]
Debt, stated interest rate	8.75%