Annual report pursuant to Section 13 and 15(d)

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

v3.6.0.2
Significant Accounting Policies Significant Accounting Policies (Disaggregated Revenue) (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Disaggregated Revenue [Line Items]                      
Revenue from operations $ 745,738 $ 782,611 $ 755,435 $ 707,733 $ 734,572 $ 779,474 $ 762,151 $ 696,245 $ 2,991,517 $ 2,972,442 $ 2,787,897
LTL Service Revenue [Member]                      
Disaggregated Revenue [Line Items]                      
Revenue from operations                 2,939,572 2,893,683 2,706,654
Other Service Revenue [Member]                      
Disaggregated Revenue [Line Items]                      
Revenue from operations                 $ 51,945 $ 78,759 $ 81,243