Revenue From Contracts With Customers - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Retained earnings opening balance sheet adjustment for Topic 606 adoption	$ 1,023,959		$ 795,698
Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Retained earnings opening balance sheet adjustment for Topic 606 adoption		$ 1,809
Contract assets	$ 3,951	$ 3,065
Accounting Standards Update 2014-09 [Member] \| Maximum [Member]
Disaggregation of Revenue [Line Items]
Term of installation services	14 days
Company's normal payment terms	60 days
Warranty period	24 months
Term of separately priced contracts	60 months
Accounting Standards Update 2014-09 [Member] \| Minimum [Member]
Disaggregation of Revenue [Line Items]
Company's normal payment terms	30 days
Warranty period	12 months
Term of separately priced contracts	12 months