Pension Plans - Net Periodic Benefit Cost (Credit) (Details) - Pension Plan [Member] - Qualified Plan [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	$ 534	$ 534	$ 1,484	$ 1,885
Expected return on plan assets	(1,103)	(962)	(3,150)	(3,071)
Amortization of net actuarial loss	217	340	801	903
Net settlement loss	443	1,343	1,009	1,343
Total net periodic pension expense	$ 91	$ 1,255	144	$ 1,060
Discount rate (as a percent)					2.31%	1.95%
Decrease in liability under the pension plan			$ (6,900)