Balance Sheet Components - Components (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
RECEIVABLES
Customers	$ 288,288	$ 298,118
Other	10,949	6,415
Total	299,237	304,533
Less allowance for doubtful accounts	6,091	6,347
Total receivables - net	293,146	298,186
INVENTORIES
Raw materials and components parts	173,248	182,382
Work in process	29,436	28,761
Finished goods	87,226	82,324
Total inventories	289,910	293,467
PROPERTY, PLANT AND EQUIPMENT
Land and improvements	33,705	32,240
Buildings and improvements	192,428	187,301
Machinery, equipment and other	430,423	397,498
Office and transportation equipment	95,549	95,759
Construction in progress	28,704	24,546
Total	780,809	737,344
Less accumulated depreciation and amortization	482,536	457,028
Total property, plant and equipment - net	298,273	280,316
ACCRUED EXPENSES
Payroll and related items	75,238	77,556
Management incentive compensation	15,763	14,408
Income taxes payable	13,453	9,905
Insurance	11,115	8,240
Warranty	7,394	5,581
Deferred revenue	28,374	17,633
Lease liability	16,721	15,235
Restructuring	3,868	6,110
Liability for uncertain tax positions	0	890
Accrued interest	3,592	1,735
Contingent consideration for acquisition	0	3,375
Other	33,310	19,622
Total accrued expenses	208,828	180,290
OTHER NONCURRENT LIABILITIES
Pension and retiree medical obligations	99,417	87,478
Transition tax payable	14,208	11,292
Liability for uncertain tax positions	1,071	3,008
Deferred revenue	30,354	2,129
Lease liability	94,250	69,928
Other	27,497	23,533
Total other noncurrent liabilities	$ 266,797	$ 197,368