Retirement Plans and Other Postretirement Benefits - Fair Value of Plan Assets (Details) - Defined Benefit Plan - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Total	$ 23,164	$ 22,090	$ 25,843	$ 25,446
Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Total	11,116	11,003
Short-term investment funds
Defined Benefit Plan Disclosure [Line Items]
Total	951	800
Level 1
Defined Benefit Plan Disclosure [Line Items]
Total	951	800
Level 1 | Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Level 1 | Short-term investment funds
Defined Benefit Plan Disclosure [Line Items]
Total	951	800
Level 2
Defined Benefit Plan Disclosure [Line Items]
Total	22,213	21,290
Level 2 | Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Total	11,116	11,003
Level 2 | Short-term investment funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Level 3 | Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Level 3 | Short-term investment funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
United States | Equity security funds
Defined Benefit Plan Disclosure [Line Items]
Total	8,883	8,198
United States | Level 1 | Equity security funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
United States | Level 2 | Equity security funds
Defined Benefit Plan Disclosure [Line Items]
Total	8,883	8,198
United States | Level 3 | Equity security funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
International | Equity security funds
Defined Benefit Plan Disclosure [Line Items]
Total	2,214	2,089
International | Level 1 | Equity security funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
International | Level 2 | Equity security funds
Defined Benefit Plan Disclosure [Line Items]
Total	2,214	2,089
International | Level 3 | Equity security funds
Defined Benefit Plan Disclosure [Line Items]
Total	$ 0	$ 0