Workers' Compensation Expense (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Reimbursable liabilities	$ 13.6
Insurance receivable, current	0.5
Insurance receivable, noncurrent	13.1
Traumatic and other workers’ compensation claims
Defined Benefit Plan Disclosure [Line Items]
Surety bonds and letters of credit outstanding	$ 121.7
Risk Free Interest Rate | Traumatic and other workers’ compensation claims
Defined Benefit Plan Disclosure [Line Items]
Discount rate	0.0175