Deferred Revenue and Advance Payments (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Deferred Revenue Disclosure [Abstract]
Deferred product licenses revenue, Current	$ 1,819	$ 3,760
Deferred subscription services revenue, Current	13,847	17,324
Deferred product support revenue, Current	151,909	168,185
Deferred other services revenue, Current	7,783	9,465
Total current deferred revenue and advance payments	175,358	198,734
Deferred product licenses revenue, Non-current	794	820
Deferred subscription services revenue, Non-current	9	126
Deferred product support revenue, Non-current	3,950	4,826
Deferred other services revenue, Non-current	1,063	628
Total non-current deferred revenue and advance payments	$ 5,816	$ 6,400