Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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Name:	us-gaap_RestructuringCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Organizational Restructuring (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring (income) expense	$ (70)	$ 1,257
2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Percentage of positions eliminated (less than for 2018)				10.00%
2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Percentage of positions eliminated (less than for 2018)			10.00%
Restructuring expected costs			$ 13,000
Restructuring (income) expense	$ (70)		$ 10,300