Commitments and Contingencies (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 06, 2015 crash_tests	Jan. 27, 2015 state
Contingencies (Textual) [Abstract]
Minimum possible loss	$ 3,900,000								$ 3,900,000
Maximum possible loss	29,300,000								29,300,000
Revenues	1,661,400,000	1,562,800,000	1,485,300,000	1,460,500,000	1,256,000,000	1,110,300,000	1,066,100,000	932,900,000	6,170,000,000	4,365,300,000	3,811,900,000
Unrestricted cash, cash equivalents, and short-term marketable securities	962,900,000				578,200,000				962,900,000	578,200,000
Available liquidity when combined with capacity under committed credit facilities	1,600,000,000								1,600,000,000
Total accrual	27,500,000								27,500,000
Unrecorded Unconditional Purchase Obligation [Line Items]
Non-cancelable purchase obligations	1,400,000,000								1,400,000,000
Raw Materials and Components | Rail, Inland Barge, and Energy Equipment Groups
Unrecorded Unconditional Purchase Obligation [Line Items]
Non-cancelable purchase obligations	1,200,000,000								1,200,000,000
Highway products litigation
Contingencies (Textual) [Abstract]
Potential amount of supersedeas bond required in excess of final judgment									20.00%
Number of additional crash tests requested	8								8
Number of class action lawsuits									2
Highway products litigation | Subsequent event
Contingencies (Textual) [Abstract]
Number of additional crash tests requested, passed to date												4
Number of states that have removed product from qualified products list													42
Highway products litigation | ET Plus
Contingencies (Textual) [Abstract]
Revenues									35,100,000	46,000,000
Highway products litigation | Joshua Harman, False Claims Act
Contingencies (Textual) [Abstract]
Damages awarded by jury verdict									175,000,000
Damages awarded by jury verdict, automatically trebled under the Act									525,000,000
Minimum possible loss	525,000,000								525,000,000
Maximum possible loss	709,000,000								709,000,000
Total accrual	0								0
Highway products litigation | Joshua Harman, False Claims Act | Minimum
Contingencies (Textual) [Abstract]
Civil penalties per violation, at the discretion of the District Court									5,500
Civil penalties, at the discretion of the District Court									5,500
Highway products litigation | Joshua Harman, False Claims Act | Maximum
Contingencies (Textual) [Abstract]
Civil penalties per violation, at the discretion of the District Court									11,000
Civil penalties, at the discretion of the District Court									184,000,000
Highway products litigation | Class Action, Illinois
Contingencies (Textual) [Abstract]
Number of counties claimed as parties to class action suit									101
Highway products litigation | Class action, Canada
Contingencies (Textual) [Abstract]
Compensatory damages sought									400,000,000
Punitive damages sought									100,000,000
Train derailment
Contingencies (Textual) [Abstract]
Number of tank cars owned by the Company and leased to third party (in railcars)									13
Number of tank cars manufactured by the Company (in railcars)									35
Number of tank cars involved in derailment (in railcars)									72
Total accrual	11,400,000								11,400,000
Expected third-party recoveries	10,200,000								10,200,000
Environmental and workplace matters
Contingencies (Textual) [Abstract]
Total accrual	$ 6,100,000								$ 6,100,000