Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net pension cost of plans
Interest cost	$ 1,813	$ 1,685
Expected return on plan assets	(1,111)	(1,524)
Recognized actuarial loss	733	689
Net periodic benefit cost	1,435	$ 850
Pension Plan
Defined Benefit Plan Disclosure
Contributions to qualified pension plan	2,200
Restoration Pension Plan
Defined Benefit Plan Disclosure
Benefits paid	$ 400