Accident and Workers' Compensation Insurance Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Excess Insurance Coverage Limit	$ 100.0
Trust fund requirements	0.7
Restricted Cash and Cash Equivalents, Noncurrent	12.4	$ 11.4
Letters of Credit Outstanding, Amount	8.6
Auto liability retention limit minimum [Member]
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Auto liability retention limit	0.5
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
Gordon Trucking Company, Inc [Member]
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Trust fund requirements	0.6
Restricted Cash and Cash Equivalents, Noncurrent	$ 0.6	$ 0.7