Supplemental Balance Sheet Information - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, at beginning of year	$ 6,098	$ 14,524	$ 19,307
Bad debt expense	3,155	1,083	6,369
Write-offs and adjustments	(3,478)	(9,509)	(11,152)
Balance, at end of year	5,775	6,098	14,524
Corrosion Protection
Allowance for Doubtful Accounts Receivable [Roll Forward]
Bad debt expense			2,900
Infrastructure Solutions
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, at beginning of year		7,500
Balance, at end of year			7,500
Restructuring Plan 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Bad debt expense	$ 400	$ (600)	$ 1,200