Accident and Workers' Compensation Insurance Liabilities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accident and Workers' Compensation Insurance Liabilities [Line Items]
Excess Insurance Coverage Limit	$ 75.0
Trust fund requirements	0.7
Restricted Cash and Cash Equivalents, Noncurrent	12.6	10.5
Restricted Cash and Investments, Noncurrent	0.6
Restricted Cash and Investments, Current		0.1
Letters of Credit Outstanding, Amount	7.5
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	0.7
Restricted Cash and Cash Equivalents, Noncurrent	$ 0.7