Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Restricted Cash and Cash Equivalents	$ 32,500	$ 21,700
Restricted Cash and Investments, Current	11,600	9,300
Restricted Cash and Cash Equivalents, Noncurrent	20,900	$ 12,400
revenue equipment [Member]
Property, Plant and Equipment [Line Items]
Restricted Cash and Cash Equivalents	5,500
Insurance Claims [Member]
Property, Plant and Equipment [Line Items]
Restricted Cash and Cash Equivalents	$ 6,100