Accounts Receivable - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts Receivable and Allowance for Doubtful Accounts [Abstract]
Accounts Receivable Gross Current	$ 213,800	$ 202,400
Accounts Receivable Greater Than 90 Days Past Due	15,200	18,000
Business Combination, Acquired Receivables, Estimated Uncollectible	$ 0	100	$ 400
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable Additional Narrative Disclosure	Included in write-offs charged to allowance during the years ended December 31, 2017 and 2016 were outstanding receivables related to certain prior year customer bankruptcies, which the Company previously reserved for, but settled during 2017 and 2016, respectively.
Customer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for Doubtful Accounts	$ 0	$ 0	$ 300