Post Retirement Benefit Plans - Assumptions (Details)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Minimum
Assumptions used to determine projected benefit obligations
Discount rate (as a percent)	0.3	0.2	0.2
Expected return on plan assets (as a percent)	0.00%	0.00%	0.00%
Expected rate of compensation increase (as a percent)	0.00%	1.00%	1.00%
Maximum
Assumptions used to determine projected benefit obligations
Discount rate (as a percent)	2.3	2.3	2.1
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%