Pension and Other Post Retirement Benefit Plans - Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Net periodic pension benefit cost	$ (909)	$ (1,693)	$ 654
Net gain (loss)	4,552	(2,189)	1,504
Amortization of net loss	404	287	1,979
Amortization of prior service cost	87	87	90
Total recognized in other comprehensive income (loss)	5,043	(1,815)	3,573
Total recognized in net periodic pension benefit cost and other comprehensive income (loss)	$ 5,952	$ (122)	$ 2,919