Commitments and Contingencies Asbestos Claimant and Settlement (Details) - Asbestos [Member]	3 Months Ended	12 Months Ended
	Mar. 31, 2019 USD ($) claimants	Dec. 31, 2018 USD ($) claimants	Dec. 31, 2017 claimants
Loss Contingencies [Line Items]
Loss Contingency, Pending Claims, Number	4,811	4,820	5,256
Loss Contingency, New Claims Filed, Number	32	171
Loss Contingency, Claims Dismissed, Number	38	564
Loss Contingency, Claims Settled, Number	3	43
Average settlement amount per claim during period | $	$ 59,300	$ 7,191
Total defense costs during period | $	$ 590,000	$ 2,260,000