Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net pension cost of plans
Interest cost	$ 1,813	$ 1,685	$ 3,626	$ 3,370
Expected return on plan assets	(1,111)	(1,524)	(2,222)	(3,047)
Recognized actuarial loss	733	689	1,466	1,377
Net periodic benefit cost	1,435	$ 850	2,870	$ 1,700
Pension Plan
Defined Benefit Plan Disclosure
Contributions to qualified pension plan	2,200		2,200
Restoration Pension Plan
Defined Benefit Plan Disclosure
Benefits paid	$ 400		$ 800