Segment Reporting (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Non-operating pension costs and share-based compensation expense	$ 46,708	$ 56,257	$ 38,978
Depreciation expense	1,255,175	1,187,050	1,121,966
Used vehicle sales, net	17,241	(972)	(99,853)
Amortization expense and other non-cash charges, net	12,114	30,667	52,965
Interest expense	140,350	147,843	150,434
Capital expenditures paid	1,860,436	1,905,157	2,667,978
Total assets	11,452,231	10,902,454	10,952,580
Acquisition payments	1,000
Operating Segments | Fleet Management Solutions
Segment Reporting Information [Line Items]
Non-operating pension costs and share-based compensation expense	5,339	5,464	5,672
Depreciation expense	1,218,492	1,156,888	1,092,750
Used vehicle sales, net	17,553	(724)	(99,758)
Amortization expense and other non-cash charges, net	29,550	34,652	36,348
Interest expense	144,137	151,297	154,276
Capital expenditures paid	1,783,917	1,814,146	2,595,961
Total assets	10,386,613	9,954,452	10,061,092
Operating Segments | Dedicated Transportation Solutions
Segment Reporting Information [Line Items]
Non-operating pension costs and share-based compensation expense	1,270	1,254	1,155
Depreciation expense	3,520	3,222	3,184
Used vehicle sales, net	(113)	(90)	(54)
Amortization expense and other non-cash charges, net	(21,967)	1,027	1,878
Interest expense	(1,659)	(1,901)	(1,597)
Capital expenditures paid	3,375	2,551	3,570
Total assets	276,832	255,845	275,634
Operating Segments | Supply Chain Solutions
Segment Reporting Information [Line Items]
Non-operating pension costs and share-based compensation expense	2,982	2,764	3,400
Depreciation expense	32,255	25,956	25,721
Used vehicle sales, net	(199)	(158)	(41)
Amortization expense and other non-cash charges, net	1,015	3,215	2,971
Interest expense	(2,446)	(1,663)	(2,174)
Capital expenditures paid	50,117	64,186	27,841
Total assets	864,022	713,190	636,647
Central Support Service
Segment Reporting Information [Line Items]
Non-operating pension costs and share-based compensation expense	37,117	46,775	28,751
Depreciation expense	908	984	311
Used vehicle sales, net	0	0	0
Amortization expense and other non-cash charges, net	3,516	(8,227)	11,768
Interest expense	318	110	(71)
Capital expenditures paid	23,027	24,274	40,606
Total assets	196,686	198,394	202,129
Eliminations
Segment Reporting Information [Line Items]
Non-operating pension costs and share-based compensation expense	0	0	0
Depreciation expense	0	0	0
Used vehicle sales, net	0	0	0
Amortization expense and other non-cash charges, net	0	0	0
Interest expense	0	0	0
Capital expenditures paid	0	0	0
Total assets	$ (271,922)	$ (219,427)	$ (222,922)