Changes in Operations and Non-operating Items Changes in Accrued Liability for Severance and Related Expenses (Details) - Employee Severance - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Severance and Related Activity Liability [Roll Forward]
Beginning balance	$ 4,576	$ 8,981
Additions	6,757	4,739
Payments	(4,721)	(9,144)
Ending balance	$ 6,612	$ 4,576