Defined Benefit Pension Plans Change in fair value of plan assets (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Defined benefit plan, change in fair value of plan assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 15,216	$ 21,567
Actual return on plan assets	400	(135)
Plan expenses, including PBGC premiums	(727)	(536)
Employer contributions	1,672	1,300
Settlements	4,873	6,186
Benefits paid	(179)	(794)
Fair value of plan assets at end of year	$ 11,509	$ 15,216
Plan for bargaining employees not covered by union pension plans [Member]
Defined benefit plan disclosure [Line Items]
Defined contribution plan, number of employees settled	94
Defined benefit plan, change in fair value of plan assets [Roll Forward]
Employer contributions	$ 522
Settlements	$ 453
Employee retirement plan [Member]
Defined benefit plan disclosure [Line Items]
Defined contribution plan, number of employees settled	224