Defined Benefit Pension Plans Change in fair value of plan assets (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Defined benefit plan, change in fair value of plan assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 7,105	$ 11,509
Actual return on plan assets	239	845
Plan expenses, including PBGC premiums	(364)	(513)
Employer contributions	10,158	4,091
Settlements	(13,118)	(8,400)
Fair value of plan assets at end of year	3,758	7,105
Defined Benefit Plan, Plan Assets, Benefits Paid	$ (262)	$ (427)
Employee retirement plan [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, number of employees settled	905