Employee's Pension and Postretirement Benefits - Amounts Accrued (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Amounts Accrued
Interest cost	$ 141	$ 105	$ 423	$ 316
Pension Plans, Defined Benefit [Member]
Amounts Accrued
Obligation, beginning of period			17,977	$ 19,003	$ 19,003
Interest cost			423		422
Actuarial gain			0		(1,448)
Obligation, end of period and unfunded status	$ 18,400		$ 18,400		$ 17,977