Employee Benefits - Assumptions (Details)		12 Months Ended
	Jan. 01, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2024
Net periodic cost
Weighted-average healthcare cost rate (as a percent)		6.00%
Retirement Plans
Benefit obligation
Discount rate (as a percent)		2.75%	3.45%	4.40%
Net periodic cost
Return on assets (as a percent)		5.50%	6.00%	6.00%
Retirement Plans | U.S.
Net periodic cost
Discount rate (as a percent)		3.45%	4.40%	3.68%
Return on assets (as a percent)		5.50%
Retirement Plans | U.S. | Subsequent event
Net periodic cost
Return on assets (as a percent)	5.00%
Retirement Plans | U.K.
Net periodic cost
Discount rate (as a percent)		1.92%	2.72%	2.41%
Return on assets (as a percent)		6.00%
Retirement Plans | U.K. | Subsequent event
Net periodic cost
Return on assets (as a percent)	5.50%
Postretirement Plans
Benefit obligation
Discount rate (as a percent)		2.20%	3.08%	4.15%
Net periodic cost
Weighted-average healthcare cost rate (as a percent)		6.00%	6.50%	6.50%
Postretirement Plans | Forecast
Net periodic cost
Weighted-average healthcare cost rate (as a percent)					5.00%
Postretirement Plans | U.S.
Net periodic cost
Discount rate (as a percent)		3.08%	4.15%	3.40%