Balance Sheet Components - Components (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
RECEIVABLES
Customers	$ 313,719		$ 297,796
Other	5,182		4,134
Total	318,901		301,930
Less allowance for doubtful accounts	6,709		7,764
Total receivables - net	312,192		294,166
INVENTORIES
Raw materials and components parts	178,805		169,676
Work in process	37,495		33,668
Finished goods	63,695		56,380
Total	279,995		259,724
PROPERTY, PLANT AND EQUIPMENT
Land and improvements	32,100		32,984
Buildings and improvements	189,744		175,467
Machinery, equipment and other	372,804		356,728
Office and transportation equipment	96,350		96,541
Construction in progress	24,328		14,715
Total	715,326		676,435
Less accumulated depreciation and amortization	434,106		418,085
Total property, plant and equipment - net	281,220		258,350
ACCRUED EXPENSES
Payroll and related items	78,944		75,869
Management incentive compensation	25,321		24,320
Income taxes payable	23,844		28,033
Insurance	10,422		9,424
Warranty	5,303		6,281
Deferred revenue	8,055		11,031
Restructuring	6,170		4,180
Liability for uncertain tax positions	980		1,745
Accrued interest	1,759		1,759
Other	26,738		22,063
Total accrued expenses	187,536		184,705
OTHER NONCURRENT LIABILITIES
Pension and retiree medical obligations	80,667		99,646
Transition tax payable	17,127		27,877
Liability for uncertain tax positions	3,183		1,047
Deferred revenue	3,027	$ 3,297	3,297
Liability for construction of new leased facility	11,616
Contingent consideration for acquisition	3,375		0
Other	19,219		23,818
Total other noncurrent liabilities	$ 138,214		$ 155,685