Discontinued Operations and Divestitures - Somar (Narrative) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Oct. 25, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain on sale of business and other assets		$ (2,866)	$ (2,763)	$ (29,859)	$ (5,074)
Somar | Disposal Group, Held-for-sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Aggregate purchase price	$ 124,000
Net gain on sale of business and other assets	$ 1,300