Assets for Each Reportable Segment (Detail) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Cash, cash equivalents and investments	$ 44,842	$ 48,238
Restricted cash	1,450	1,602
Deferred income taxes	3	3
Other current assets	1,001	997
Common property, plant and equipment	1,608	1,039
Other assets	671	871
Consolidated total assets	108,728	108,324
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated total assets	59,153	55,574
Operating Segments | Thin-film Equipment Segment
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated total assets	41,862	39,503
Operating Segments | Photonics
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated total assets	$ 17,291	$ 16,071