Changes in Operations Freightliner Fair Values Assigned to Acquired Net Assets (Details)			3 Months Ended
	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Mar. 31, 2015 Freightliner [Member]	Mar. 25, 2015 Freightliner [Member] USD ($)	Mar. 25, 2015 Freightliner [Member] GBP (£)
Cash and cash equivalents				$ 50,371,000	£ 33,815,000
Accounts receivable				75,271,000	50,531,000
Materials and supplies				14,509,000	9,740,000
Prepaid expenses and other				22,818,000	15,318,000
Property and equipment				239,081,000	160,500,000
Goodwill	907,440,000	628,815,000		287,911,000	193,281,000
Intangible assets				536,405,000	360,100,000
Other assets				523,000	351,000
Total assets				1,226,889,000	823,636,000
Current portion of long-term debt				20,774,000	13,946,000
Accounts payable and accrued expenses				135,913,000	91,241,000
Long-term debt, less current portion				59,194,000	39,738,000
Deferred income tax liabilities, net				191,658,000	128,664,000
Deferred items-grants from outside parties				1,248,000	838,000
Other long-term liabilities				49,409,000	33,169,000
Net assets				768,693,000	516,040,000
Weighted average amortization period of amortizable intangible assets acquired			85 years
Expected tax deductible amount of goodwill				0
Pension liability included with assumed other long-term liabilities				$ 36,800,000	£ 24,700,000