Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets
Pension liabilities	$ 85.3	$ 62.1
Retirement benefits other than pensions	67.5	61.2
Lease liabilities	72.3	62.8
Workers’ compensation and other claims	35.6	37.0
Property and equipment, net	39.2	31.0
Other assets and liabilities	108.7	93.6
Net operating loss carryforwards	74.8	51.7
Foreign tax and other tax credits(a)	81.6	76.8
Subtotal	565.0	476.2
Valuation allowances	(128.1)	(118.3)	$ (100.7)	$ (98.9)
Total deferred tax assets	436.9	357.9
Deferred tax liabilities
Right-of-use assets, net	68.3	59.3
Goodwill and other intangibles	60.0	17.4
Other assets and miscellaneous	36.4	28.9
Deferred tax liabilities	164.7	105.6
Net deferred tax asset	272.2	252.3
Noncurrent assets	314.9	273.5
Noncurrent liabilities	(42.7)	$ (21.2)
Operating Loss Carryforwards [Line Items]
Foreign tax credit amount	77.4
Remaining credits	4.2
Foreign
Deferred tax assets
Net operating loss carryforwards	$ 59.2
Operating Loss Carryforwards [Line Items]
Carryforward period (in years)	10 years