Balance Sheet Components - Components (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
RECEIVABLES
Customers	$ 297,796	$ 275,250
Other	4,134	5,641
Total	301,930	280,891
Less allowance for doubtful accounts	7,764	8,078
Total receivables — net	294,166	272,813
INVENTORIES
Raw materials and components parts	169,676	154,278
Work in process	33,668	34,832
Finished goods	56,380	63,749
Total	259,724	252,859
PROPERTY, PLANT AND EQUIPMENT
Land and improvements	32,984	33,883
Buildings and improvements	175,467	169,261
Machinery, equipment and other	356,728	328,779
Office and transportation equipment	96,541	98,355
Construction in progress	14,715	10,373
Total	676,435	640,651
Less accumulated depreciation and amortization	418,085	392,835
Total property, plant and equipment — net	258,350	247,816
ACCRUED EXPENSES
Payroll and related items	75,869	67,600
Management incentive compensation	24,320	16,339
Income taxes payable	28,033	8,808
Insurance	9,424	9,416
Warranty	6,281	5,628
Deferred revenue	11,031	12,607
Restructuring	4,180	3,893
Liability for uncertain tax positions	1,745	1,366
Accrued interest	1,759	1,663
Other	22,063	25,532
Total accrued expenses	184,705	152,852
OTHER NONCURRENT LIABILITIES
Pension and retiree medical obligations	99,646	93,604
Transition tax payable	27,877	0
Liability for uncertain tax positions	1,047	2,623
Deferred revenue	3,297	2,442
Other	23,818	22,561
Total other noncurrent liabilities	$ 155,685	$ 121,230