Long-term debt - Effects of Interest Rate Swap and Cap Agreements (Detail) - Cash Flow Hedging - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments Gain Loss [Line Items]
Amount of unrealized losses in OCI on interest rate cap agreements	$ (1,628)	$ (1,060)	$ (16,470)	$ (1,672)
Reclassification from accumulated other comprehensive loss into net income	1,034	1,569	4,280	4,782
Related income tax
Derivative Instruments Gain Loss [Line Items]
Amount of unrealized losses in OCI on interest rate cap agreements	541	360	5,476	572
Reclassification from accumulated other comprehensive loss into net income	(344)	(532)	(1,424)	(1,646)
Interest rate cap agreements | Debt Expense
Derivative Instruments Gain Loss [Line Items]
Amount of unrealized losses in OCI on interest rate cap agreements	(2,169)	(1,420)	(21,946)	(2,244)
Reclassification from accumulated other comprehensive loss into net income	$ 1,378	$ 2,101	$ 5,704	$ 6,428