Employee Benefit Obligations - Asset Categories (Details)	Dec. 31, 2022	Dec. 31, 2021
United States | Minimum | Fixed income securities
Target asset allocations
Target asset allocations (as a percent)	40.00%
United States | Minimum | Equity securities
Target asset allocations
Target asset allocations (as a percent)	20.00%
United States | Minimum | Alternative investments
Target asset allocations
Target asset allocations (as a percent)	5.00%
United States | Maximum | Fixed income securities
Target asset allocations
Target asset allocations (as a percent)	70.00%
United States | Maximum | Equity securities
Target asset allocations
Target asset allocations (as a percent)	40.00%
United States | Maximum | Alternative investments
Target asset allocations
Target asset allocations (as a percent)	25.00%
U.K. | Minimum | Fixed Income Securities And Cash And Cash Equivalents Combined
Target asset allocations
Target asset allocations (as a percent)	80.00%
U.K. | Minimum | Cash and cash equivalents
Target asset allocations
Target asset allocations (as a percent)	80.00%
U.K. | Minimum | Fixed income securities
Target asset allocations
Target asset allocations (as a percent)	80.00%
U.K. | Minimum | Equity securities
Target asset allocations
Target asset allocations (as a percent)	0.00%
U.K. | Maximum | Fixed Income Securities And Cash And Cash Equivalents Combined
Target asset allocations
Target asset allocations (as a percent)	100.00%
U.K. | Maximum | Cash and cash equivalents
Target asset allocations
Target asset allocations (as a percent)	100.00%
U.K. | Maximum | Fixed income securities
Target asset allocations
Target asset allocations (as a percent)	100.00%
U.K. | Maximum | Equity securities
Target asset allocations
Target asset allocations (as a percent)	15.00%
Defined Benefit Pension Plans
Target asset allocations
Weighted average asset allocations (as a percent)	100.00%	100.00%
Defined Benefit Pension Plans | Cash and cash equivalents
Target asset allocations
Weighted average asset allocations (as a percent)	2.00%
Defined Benefit Pension Plans | Fixed income securities
Target asset allocations
Weighted average asset allocations (as a percent)	77.00%	81.00%
Defined Benefit Pension Plans | Equity securities
Target asset allocations
Weighted average asset allocations (as a percent)	16.00%	17.00%
Defined Benefit Pension Plans | Alternative investments
Target asset allocations
Weighted average asset allocations (as a percent)	5.00%	2.00%