Debt - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Debt Instrument [Line Items]
Capitalized interest costs	$ 300,000	$ 300,000	$ 500,000	$ 600,000
Cash paid for debt issuance or prepayment costs			(16,703,000)	(38,130,000)
Gain (loss) on extinguishment of debt	(12,938,000)	$ (39,639,000)	(12,938,000)	$ (39,639,000)
Reduction of long-term debt	1,092,174,000		1,092,174,000		$ 828,565,000
Senior Secured Revolving Facility [Member]
Debt Instrument [Line Items]
Senior debt	67,962,000		$ 67,962,000		0
Senior Secured Revolving Facility [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt maturity date			Oct. 19, 2020
Applicable margin			3.50%
Second Lien Credit Agreement [Member]
Debt Instrument [Line Items]
Senior debt	200,000,000		$ 200,000,000		$ 0
Cash paid for debt issuance or prepayment costs			(16,700,000)
Gain (loss) on extinguishment of debt			(12,900,000)
Reduction of long-term debt	3,800,000		3,800,000
Second Lien Credit Agreement [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Borrowings	$ 200,000,000		$ 200,000,000
Debt maturity date			Apr. 19, 2023
Applicable margin			8.00%
Second Lien Credit Agreement [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate	1.00%		1.00%