Intangible Assets and Goodwill Goodwill (Details) £ in Millions	12 Months Ended
	Dec. 31, 2017 GBP (£)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Goodwill, Gross		$ 1,180,069,000	$ 1,140,078,000	$ 826,575,000
Balance at beginning of period		1,125,596,000
Goodwill acquired		15,179,000	335,236,000
Acquisition accounting adjustments		(22,415,000)	10,080,000
Currency translation adjustment		47,227,000	(31,813,000)
Goodwill impairment		0	(14,482,000)	0
Goodwill, Impaired, Accumulated Impairment Loss		(14,482,000)	(14,482,000)
Balance at end of period		1,165,587,000	1,125,596,000
North American Operations [Member]
Segment Reporting Information [Line Items]
Goodwill, Gross		638,010,000	632,937,000	605,234,000
Balance at beginning of period		632,937,000
Goodwill acquired		4,083,000	26,969,000
Acquisition accounting adjustments		(650,000)	176,000
Currency translation adjustment		1,640,000	558,000
Goodwill impairment			0
Goodwill, Impaired, Accumulated Impairment Loss		0	0
Balance at end of period		638,010,000	632,937,000
Australian Operations [Member]
Segment Reporting Information [Line Items]
Goodwill, Gross		367,368,000	339,865,000	39,312,000
Balance at beginning of period		339,865,000
Goodwill acquired		0	308,267,000
Acquisition accounting adjustments		0	168,000
Currency translation adjustment		27,503,000	(7,882,000)
Goodwill impairment			0
Goodwill, Impaired, Accumulated Impairment Loss		0	0
Balance at end of period		367,368,000	339,865,000
U.K./European Operations [Member]
Segment Reporting Information [Line Items]
Goodwill, Gross		174,691,000	167,276,000	$ 182,029,000
Balance at beginning of period		152,794,000
Goodwill acquired		11,096,000	0
Acquisition accounting adjustments		(21,765,000)	9,736,000
Currency translation adjustment		18,084,000	(24,489,000)
Goodwill impairment			(14,482,000)
Goodwill, Impaired, Accumulated Impairment Loss		(14,482,000)	14,482,000
Balance at end of period		160,209,000	$ 152,794,000
Freightliner [Member] | U.K./European Operations [Member]
Segment Reporting Information [Line Items]
Changes in tax basis of assets acquired | £	£ 43.8
Change in tax basis [Member] | Freightliner [Member] | U.K./European Operations [Member]
Segment Reporting Information [Line Items]
Acquisition accounting adjustments		(10,400,000)
Deferred Income Tax Liabilities, Purchase Accounting Adjustment		10,400,000
Prepaid maintenance cost [Member] | Freightliner [Member] | U.K./European Operations [Member]
Segment Reporting Information [Line Items]
Acquisition accounting adjustments		(11,300,000)
Deferred Income Tax Liabilities, Purchase Accounting Adjustment		(2,300,000)
Other Assets, Purchase Accounting Adjustment		$ 13,600,000