Quarterly report pursuant to Section 13 or 15(d)

Significant Accounting Policies Significant Accounting Policies (Disaggregated Revenue) (Details)

v3.8.0.1
Significant Accounting Policies Significant Accounting Policies (Disaggregated Revenue) (Details) - USD ($)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Disaggregated Revenue [Line Items]    
Revenue from operations $ 925,020,000 $ 754,096,000
LTL Service Revenue [Member]    
Disaggregated Revenue [Line Items]    
Revenue from operations 911,054,000 740,186,000
Other Service Revenue [Member]    
Disaggregated Revenue [Line Items]    
Revenue from operations $ 13,966,000 $ 13,910,000