Retirement Plans - Assumptions Used to Determine the Benefit Obligation (Details) - Pension Plans, Defined Benefit	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net benefit obligation
Discount rate	1.86%	2.14%
Rate of increases in compensation level	4.33%	4.39%
Weighted average
Net periodic benefit cost
Discount rate	2.14%	2.06%
Rate of increases in compensation level	4.39%	4.30%
Expected long-term rate of return on assets	3.49%	3.81%
Minimum
Net periodic benefit cost
Discount rate			0.50%
Rate of increases in compensation level			2.00%
Expected long-term rate of return on assets			0.75%
Maximum
Net periodic benefit cost
Discount rate			3.90%
Rate of increases in compensation level			5.00%
Expected long-term rate of return on assets			6.00%