Segments - Reconciliation of Total Segment EBITDA to Income Before Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting [Abstract]
Total Segment EBITDA	$ 59,774	$ 47,575
Depreciation and amortization	9,907	8,465
Other income (expense)	(3,318)	192
Income from operations	53,185	38,918
Interest income	1,798	37
Interest expense	(14,749)	(8,771)
Income before income taxes	$ 36,916	$ 30,376