Defined Benefit Post-Retirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Post-Retirement Plans [Abstract]
Employer contributions	$ 0	$ 0	$ 0	$ 0
Pension Benefits [Member]
Components of net periodic cost (benefit) [Abstract]
Service cost	431	415	1,301	1,256
Interest cost	986	912	2,948	2,752
Expected return on plan assets	(1,869)	(2,119)	(5,615)	(6,364)
Net amortization	658	242	1,936	745
Total net periodic cost (benefit)	206	(550)	570	(1,611)
Other Benefits [Member]
Components of net periodic cost (benefit) [Abstract]
Service cost	1	3	5	8
Interest cost	67	82	229	245
Expected return on plan assets	0	0	0	0
Net amortization	14	44	49	131
Total net periodic cost (benefit)	$ 82	$ 129	$ 283	$ 384