Pension Plans - Net Periodic Benefit Cost (Credit) (Details) - Pension Plan [Member] - Qualified Plan [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	$ 478	$ 675	$ 950	$ 1,351
Expected return on plan assets	(1,028)	(1,054)	(2,047)	(2,109)
Amortization of net actuarial loss	295	281	584	563
Net settlement loss	566		566
Total net periodic pension expense (benefit)	$ 311	$ (98)	$ 53	$ (195)
Discount rate (as a percent)	2.31%		2.31%		1.95%
Decrease in liability under the pension plan			$ (6,900)