Deferred Revenue and Customer Advances (Detail) - USD ($) $ in Thousands	Apr. 01, 2018	Jan. 01, 2018	Dec. 31, 2017	Apr. 02, 2017	Dec. 31, 2016
Deferred Revenue Arrangement
Maintenance and training	$ 59,365		$ 57,256
Extended warranty	24,590	$ 24,438	24,438	$ 24,969	$ 28,200
Customer advances, undelivered elements and other	23,663		32,047
Total deferred revenue and customer advances	$ 107,618		$ 113,741