Employee Benefit Plans - Plan assets using fair value hierarchy (Details) - Retirement Income Plan - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Investments measured at Net Asset Value	$ 2,821	$ 3,600
Investments at Fair Value	40,142	38,364
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	505	1,140
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	36,813	11,163
Domestic Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	3	15,182
International Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy		7,279
Investment
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	37,321	34,764
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	505	1,140
Level 1 | Domestic Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	3	5,602
Level 1 | Investment
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	508	6,742
Level 2 | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	36,813	11,163
Level 2 | Domestic Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy		9,581
Level 2 | International Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy		7,279
Level 2 | Investment
Defined Benefit Plan Disclosure [Line Items]
Total Assets in the Fair Value Hierarchy	$ 36,813	$ 28,023