Pension Plans - Net Periodic Benefit Cost (Credit) (Details) - Pension Plan [Member] - Qualified Plan [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	$ 472	$ 676
Expected return on plan assets	(1,019)	(1,055)
Amortization of net actuarial loss	289	282
Total net periodic benefit expense (income)	$ (258)	$ (97)