Accident and Workers' Compensation Insurance Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Excess Insurance Coverage Limit	$ 100.0
Trust fund requirements	0.7
Debt Securities, Held-to-maturity	1.5	$ 1.5
Letters of Credit Outstanding, Amount	12.8
Letter of credit due	0.0	$ 0.0
Excess Insurance Coverage Minimum Claims	3.0
Excess Insurance Coverage Maximum Claims	10.0
Aggregate Self-Insurance Corridor	1.0
Aggregate Self-Insurance Corridor Claims Minimum [Member]	2.0
Aggregate Self-Insurance Corridor Claims Maximum [Member]	3.0
Auto liability retention limit minimum [Member]
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Auto liability retention limit	0.1
Auto liability retention limit maximum [Member] [Member]
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Auto liability retention limit	2.0
workers compensation retention limit minimum [Member]
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Workers compensation retention limit	0.5
workers compensation retention limit maximum [Member]
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Workers compensation retention limit	$ 1.0