Segment Information (Tables)

6 Months Ended

Jun. 30, 2019

Segment Reporting [Abstract]

Reconciliation of Revenue from Segments to Consolidated [Table Text Block]

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2019		2018		2019		2018
Revenues
Truckload	$	374,405	$	391,397	$	743,524	$	762,564
Brokerage		39,457		58,361		85,701		112,902
Total Operating Revenue	$	413,862	$	449,758	$	829,225	$	875,466
Operating Income
Truckload	$	7,503	$	18,590	$	17,344	$	31,093
Brokerage		1,284		1,428		4,081		3,779
Total Operating Income	$	8,787	$	20,018	$	21,425	$	34,872

Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2019		2018		2019		2018
Revenues
United States	$	413,862	$	436,227	$	826,853	$	849,078
Foreign countries
Mexico		—		13,531		2,372		26,388
Total	$	413,862	$	449,758	$	829,225	$	875,466