Deferred Revenue and Advance Payments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Deferred Revenue Disclosure [Abstract]
Deferred product licenses revenue, Current	$ 584	$ 3,760
Deferred subscription services revenue, Current	11,736	17,324
Deferred product support revenue, Current	131,185	168,185
Deferred other services revenue, Current	7,538	9,465
Total current deferred revenue and advance payments	151,043	198,734
Deferred product licenses revenue, Non-current	730	820
Deferred subscription services revenue, Non-current	0	126
Deferred product support revenue, Non-current	3,701	4,826
Deferred other services revenue, Non-current	492	628
Total non-current deferred revenue and advance payments	$ 4,923	$ 6,400