Supplemental Balance Sheet Information - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Allowance for doubtful accounts receivable, write-offs	$ 4,268	$ 3,478	$ 9,509
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, at beginning of year	5,775	6,098	14,524
Bad debt expense	8,188	3,155	1,083
Write-offs and adjustments	(4,268)	(3,478)	(9,509)
Balance, at end of year	9,695	5,775	6,098
Infrastructure Solutions
Segment Reporting Information [Line Items]
Allowance for doubtful accounts receivable, write-offs			7,500
Allowance for Doubtful Accounts Receivable [Roll Forward]
Write-offs and adjustments			(7,500)
Restructuring Plan 2016 and Restructuring Plan 2017
Allowance for Doubtful Accounts Receivable [Roll Forward]
Bad debt expense	$ 5,300	$ 400	$ (600)