Segment Information - Schedule of Reconciliation of Net Income to EBITDA (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net income (loss)	$ 25,171	$ 29,471	$ 42,820	$ 37,110	$ 18,299	$ 20,098	$ 28,782	$ 27,949	$ 134,572	$ 95,128	$ 67,847
Interest (income) expense, net									192	(461)	(1,125)
Taxes									42,289	46,791	34,983
Depreciation and amortization									16,597	16,860	$ 14,498
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net income (loss)									134,572	95,128
Interest (income) expense, net									(192)	461
Taxes									42,289	46,791
Depreciation and amortization									16,467	16,730
EBITDA									193,136	159,110
Operating Segments [Member] | Residential [Member]
Segment Reporting Information [Line Items]
Net income (loss)									131,823	97,412
Interest (income) expense, net									(192)	461
Taxes									41,421	47,911
Depreciation and amortization									13,216	14,598
EBITDA									186,268	160,382
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net income (loss)									2,749	(2,284)
Taxes									868	(1,120)
Depreciation and amortization									3,251	2,132
EBITDA									$ 6,868	$ (1,272)