Long-term debt - Schedule of Long-term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total debt, excluding deferred financing costs	$ 1,197,000		$ 709,470
Deferred financing costs, net of accumulated amortization	(24,873)		(5,709)
Total debt	1,172,127		703,761
Current portion of long-term debt and Variable Funding Note	12,000	$ 7,185	7,185
Long-term debt, net of current maturities	1,160,127	$ 696,576	696,576
Class A-2-I notes | Senior Notes
Debt Instrument [Line Items]
Total debt, excluding deferred financing costs	573,563		0
Class A-2-II notes | Senior Notes
Debt Instrument [Line Items]
Total debt, excluding deferred financing costs	623,437		0
Term loan B, repaid August 2018 | Loans Payable
Debt Instrument [Line Items]
Total debt, excluding deferred financing costs	$ 0		$ 709,470