Post-Retirement Benefit Plans - Benefit Obligation Assumptions (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Compensation rate increase	2.75%	3.00%
Discount rate	1.50%	1.25%
Employee turn-over description	Actuarial standard and average of the last 5 years	Actuarial standard and average of the last 5 years
Employee turn-over, average years	5 years	5 years
Average age of retirement description	60 to 65 years actuarial standard based on age and professional status	60 to 65 years actuarial standard based on age and professional status
Minimum
Defined Benefit Plan Disclosure [Line Items]
Average age of retirement (in years)	60 years	60 years
Maximum
Defined Benefit Plan Disclosure [Line Items]
Average age of retirement (in years)	65 years	65 years