Summary of Restructuring Costs for Each Segment and Unallocated Corporate Costs (Details) - USD ($) $ in Thousands	12 Months Ended			18 Months Ended	73 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2017
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	$ 2,025	$ 346	$ 2,970
2018 Restructuring
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	1,647
2018 Restructuring | Minimum
Restructuring Cost And Reserve [Line Items]
Expected Cumulative Costs	2,400
2018 Restructuring | Maximum
Restructuring Cost And Reserve [Line Items]
Expected Cumulative Costs	2,700
2018 Restructuring | Vision
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	1,579
2018 Restructuring | Vision | Minimum
Restructuring Cost And Reserve [Line Items]
Expected Cumulative Costs	2,300
2018 Restructuring | Vision | Maximum
Restructuring Cost And Reserve [Line Items]
Expected Cumulative Costs	2,600
2018 Restructuring | Unallocated Corporate and Shared Services
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	68
2018 Restructuring | Unallocated Corporate and Shared Services | Minimum
Restructuring Cost And Reserve [Line Items]
Expected Cumulative Costs	$ 100
2016 Restructuring
Restructuring Cost And Reserve [Line Items]
Restructuring Costs		332	3,049
Cumulative Costs				$ 6,529
2016 Restructuring | Photonics
Restructuring Cost And Reserve [Line Items]
Restructuring Costs			813
Cumulative Costs				868
2016 Restructuring | Vision
Restructuring Cost And Reserve [Line Items]
Restructuring Costs		331	1,862
Cumulative Costs				4,393
2016 Restructuring | Precision Motion
Restructuring Cost And Reserve [Line Items]
Restructuring Costs			106
Cumulative Costs				939
2016 Restructuring | Unallocated Corporate and Shared Services
Restructuring Cost And Reserve [Line Items]
Restructuring Costs		1	268
Cumulative Costs				$ 329
2011 Restructuring
Restructuring Cost And Reserve [Line Items]
Restructuring Costs		14	(79)
Cumulative Costs					$ 5,197
2011 Restructuring | Photonics
Restructuring Cost And Reserve [Line Items]
Restructuring Costs			(188)
Cumulative Costs					1,751
2011 Restructuring | Vision
Restructuring Cost And Reserve [Line Items]
Cumulative Costs					48
2011 Restructuring | Precision Motion
Restructuring Cost And Reserve [Line Items]
Cumulative Costs					122
2011 Restructuring | Unallocated Corporate and Shared Services
Restructuring Cost And Reserve [Line Items]
Restructuring Costs		$ 14	$ 109
Cumulative Costs					$ 3,276