Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Components of net periodic benefit cost [Abstract]
Contribution made to pension and postretirement plans			$ 0
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	$ 13	$ 6	21	$ 17
Interest cost	307	273	622	599
Expected return on plan assets	(654)	(819)	(1,406)	(1,506)
Amortization of net loss (gain)	30	(17)	30	0
Amortization of prior service cost	0	0	0	0
Net periodic benefit	(304)	(557)	(733)	(890)
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	14	26	32	52
Interest cost	60	55	120	109
Expected return on plan assets	(247)	(191)	(495)	(381)
Amortization of net loss (gain)	(50)	(89)	(98)	(178)
Amortization of prior service cost	(82)	22	(167)	45
Net periodic benefit	$ (305)	$ (177)	$ (608)	$ (353)