Segment Information - Income from Segments to Consolidated Net Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting [Abstract]
Total EBITDA	$ 46,474	$ 47,371	$ 96,912	$ 95,064
Less
Income tax expense	3,112	4,068	7,047	6,088
Interest expense, net	7,501	7,190	15,023	14,041
Depreciation and amortization	15,728	15,899	31,595	31,583
Net income	$ 20,133	$ 20,214	$ 43,247	$ 43,352