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, 2016	Dec. 31, 2015
Severance and Related Activity Liability [Roll Forward]
Beginning balance	$ 3,595	$ 1,357
Additions	10,406	5,276
Payments	(5,020)	(3,038)
Ending balance	$ 8,981	$ 3,595