Post Retirement Benefit Plans - Assumptions (Details)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Minimum
Assumptions used to determine projected benefit obligations
Discount rate (as a percent)	0.10%	0.30%	0.20%
Expected return on plan assets (as a percent)	0.00%	0.00%	0.00%
Expected rate of compensation increase (as a percent)	0.00%	0.00%	1.00%
Maximum
Assumptions used to determine projected benefit obligations
Discount rate (as a percent)	1.30%	2.30%	2.30%
Expected return on plan assets (as a percent)	3.00%	3.00%	3.00%
Expected rate of compensation increase (as a percent)	3.00%	3.00%	3.00%