Contingencies (Details Textual) guard_rail in Thousands			1 Months Ended	2 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 23, 2015 USD ($)	Jun. 09, 2015 USD ($)	Jul. 31, 2013 Railcar	Oct. 31, 2015 crash_test	Sep. 30, 2015 USD ($) state	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) state crash_test lawsuit county	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Mar. 11, 2015 guard_rail	Oct. 20, 2014 crash_test
Loss Contingencies [Line Items]
Revenues					$ 1,542,200,000	$ 1,562,800,000	$ 4,845,700,000	$ 4,508,600,000
Minimum possible loss					7,000,000		7,000,000
Maximum possible loss					26,800,000		26,800,000
Accrued liabilities
Loss Contingencies [Line Items]
Total accruals					29,300,000		29,300,000
Subsequent event
Loss Contingencies [Line Items]
Number of crash tests performed by VDOT | crash_test				6
Construction Products Group
Loss Contingencies [Line Items]
Revenues					$ 151,100,000	$ 168,400,000	$ 411,400,000	$ 430,500,000
Highway Products Litigation
Loss Contingencies [Line Items]
Number of additional crash tests requested | crash_test												8
Number of additional crash tests passed, first installation height | crash_test												4
Number of additional crash tests passed, second installation height | crash_test												4
Number of ET Plus devices field measured by FHWA engineers (more than) | guard_rail											1
Highway Products Litigation | ET Plus
Loss Contingencies [Line Items]
Number of states that have removed product from qualified products list | state					40		40
Highway Products Litigation | UNITED STATES | Construction Products Group | ET Plus
Loss Contingencies [Line Items]
Revenues							$ 0		$ 35,100,000	$ 46,000,000
Highway Products Litigation | UNITED STATES | Construction Products Group | ET Plus | ET Plus concentration | Revenues
Loss Contingencies [Line Items]
Concentration percentage									0.60%	1.10%
Highway Products Litigation | False Claims Act, USA
Loss Contingencies [Line Items]
Damages awarded by jury verdict		$ 175,000,000
Total amount of judgment entered by the District Court		682,400,000
Damages awarded by jury verdict, automatically trebled under the Act		525,000,000
Civil penalties included in judgment entered by the District Court		138,400,000
Costs and attorney's fees included in judgment entered by the District Court		$ 19,000,000
Amount of supersedeas bond posted	$ 686,000,000
Initial annual premium of supersedeas bond	$ 3,900,000
Total accruals					$ 0		0
Highway Products Litigation | State, county, and municipal actions
Loss Contingencies [Line Items]
Total accruals					0		$ 0
Number of additional separate state qui tam actions filed | lawsuit							5
Number of class action lawsuits | crash_test							3
Number of other counties claimed as parties to class action suit | county							101
Compensatory damages sought							$ 400,000,000
Punitive damages sought							100,000,000
Highway Products Litigation | Class Action, Shareholder
Loss Contingencies [Line Items]
Total accruals					0		0
Train Derailment
Loss Contingencies [Line Items]
Number of tank cars manufactured by the Company | Railcar			35
Number of tank cars involved in derailment | Railcar			72
Train Derailment | Yannick Gagne and Guy Oullet vs. Rail World, Inc
Loss Contingencies [Line Items]
Number of tank cars owned by the Company and leased to third party | Railcar			13
Environmental and workplace matters
Loss Contingencies [Line Items]
Total accruals					$ 5,000,000		$ 5,000,000