Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of net periodic benefit cost:
Service cost	$ 910	$ 548	$ 614
Interest cost	1,794	1,107	1,192
Expected return on plan assets	(1,972)	(1,258)	(1,189)
Amortization of net loss	95	0	0
Amortization of prior service cost	3	0	0
Net periodic benefit cost	$ 830	$ 397	$ 617