Employee Benefits - Weighted-average assumptions used to determine the net periodic benefit cost (Details) - Pension Plan	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets, net of administration expenses	7.04%	7.05%	7.71%
U.S. | Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	2.36%	3.92%	3.27%
Expected return on plan assets, net of administration expenses	3.30%
U.S. | Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	2.76%	4.26%	3.61%
Expected return on plan assets, net of administration expenses	7.04%
U.K.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	1.89%	2.95%	2.63%
Expected return on plan assets, net of administration expenses	2.74%	3.64%	3.34%
U.K. | Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Rate of compensation increase	3.24%	3.73%	3.70%
U.K. | Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Rate of compensation increase	3.74%	4.23%	4.20%
Other | Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	0.74%	1.89%	1.78%
Expected return on plan assets, net of administration expenses	2.10%	2.50%	1.70%
Rate of compensation increase	1.00%	1.00%	1.00%
Other | Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	2.90%	3.88%	3.39%
Expected return on plan assets, net of administration expenses	3.10%	4.10%	4.85%
Rate of compensation increase	3.00%	3.00%	3.00%