Pension Plans - Qualified Plan - Net Periodic Pension Expense (Details) - Pension Plan [Member] - Qualified Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	$ 1,969	$ 2,713	$ 2,829
Expected return on plan assets	(4,101)	(3,849)	(4,363)
Recognized net actuarial loss	1,004	970	750
Net settlement loss	1,740	1,904	1,559
Total net periodic benefit expense (income)	$ 612	$ 1,738	$ 775