Contingencies - Rollforward of Remediation Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Contingencies
Accrued liabilities start of period	$ 17,067	$ 18,176	$ 20,603
Remediation expense	1,182	307	556
Remediation payments	(6,967)	(1,416)	(2,983)
Accrued liabilities end of period	11,274	$ 17,067	$ 18,176
Accrual for Environmental Loss Contingencies, Foreign Currency Translation Gain (Loss)	$ (8)