Pension and Other Postretirement Benefits (Details 10) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pensions [Member]
Pension and other postretirement benefits expenses
Service cost	$ 5,425	$ 5,961	$ 6,055
Interest cost	18,239	17,383	18,819
Expected return on plan assets	(29,425)	(29,900)	(28,082)
Amortization of prior service cost	404	560	446
Recognized losses	8,889	11,628	10,557
Curtailment loss gain	0	0	(7,217)
Settlement loss	340	0	(119)
Net periodic benefit cost	3,872	5,632	459
Other Postretirement Benefits [Member]
Pension and other postretirement benefits expenses
Service cost	70	85	83
Interest cost	1,345	1,358	1,561
Expected return on plan assets	0	0	0
Amortization of prior service cost	25	20	(68)
Recognized losses	13	561	276
Curtailment loss gain	0	0	0
Settlement loss	0	0	0
Net periodic benefit cost	$ 1,453	$ 2,024	$ 1,852