Employee Benefit Plans - Plan assets using fair value hierarchy (Details) - Retirement Income Plan - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Investments measured at Net Asset Value	$ 0	$ 2,821
Investments at Fair Value	39,068	40,142
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	736	505
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	38,332	36,813
Domestic Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy		3
Investment
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	39,068	37,321
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	736	505
Level 1 | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	0
Level 1 | Domestic Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy		3
Level 1 | Investment
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	736	508
Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	0
Level 2 | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	38,332	36,813
Level 2 | Investment
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	$ 38,332	$ 36,813