Commitments and Contingencies - Commitments and Contingencies			3 Months Ended								12 Months Ended
	Jun. 23, 2015 USD ($)	Jun. 09, 2015 USD ($)	Dec. 31, 2017 USD ($) state	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) state lawsuit county	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 16, 2016 briefs	Mar. 28, 2016 briefs	Mar. 11, 2015 guard_rail	Oct. 20, 2014 crash_test
Loss Contingencies [Line Items]
Revenues			$ 906,400,000	$ 973,600,000	$ 905,500,000	$ 877,300,000	$ 1,103,800,000	$ 1,111,700,000	$ 1,184,900,000	$ 1,187,900,000	$ 3,662,800,000	$ 4,588,300,000	$ 6,392,700,000
Non-cancelable purchase obligations			724,000,000								724,000,000
Accrued liabilities
Loss Contingencies [Line Items]
Total accrual			17,800,000								17,800,000
Construction Products Group
Loss Contingencies [Line Items]
Revenues											498,900,000	510,600,000	$ 520,600,000
Rail Inland Barge and Energy Equipment Groups | Inventories
Loss Contingencies [Line Items]
Non-cancelable purchase obligations			$ 602,800,000								$ 602,800,000
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 Additional Crash Tests Requested Passed | crash_test																	8
Number of devices field measured (more than) | guard_rail																1,000
Highway products litigation | ET Plus
Loss Contingencies [Line Items]
Number of states that have removed product from qualified products list | state			29								29
Highway products litigation | ET Plus | UNITED STATES
Loss Contingencies [Line Items]
Revenues											$ 4,200,000	$ 4,100,000
Environmental and workplace matters
Loss Contingencies [Line Items]
Total accrual			$ 3,300,000								3,300,000
Joshua Harman, False Claims Act | Highway products litigation
Loss Contingencies [Line Items]
Damages awarded by jury verdict		$ 175,000,000
Judgment entered		682,400,000
Damages awarded by jury verdict, automatically trebled under the Act		525,000,000
Judgment entered, civil penalties		138,400,000
Judgment entered, costs and attorney fees		$ 19,000,000
Supersedeas bond posted	$ 686,000,000
Supersedeas bond, initial annual premium	$ 3,700,000
Number of amicus curiae briefs filed seeking judgment reversal | briefs															6
Number of amicus curiae briefs filed in opposition of Company's appeal | briefs														6
Total accrual			0								0
State, county, and municipal actions | Highway products litigation
Loss Contingencies [Line Items]
Total accrual			0								$ 0
Number of additional state qui tam actions filed (in lawsuits) | lawsuit											12
Number of class action lawsuits | lawsuit											2
Number of counties claimed as parties to class action suit | county											101
Compensatory damages sought											$ 400,000,000
Punitive damages sought											100,000,000
Shareholder class actions | Highway products litigation
Loss Contingencies [Line Items]
Total accrual			0								0
Minimum
Loss Contingencies [Line Items]
Range of reasonably possible losses			4,400,000								4,400,000
Maximum
Loss Contingencies [Line Items]
Range of reasonably possible losses			$ 27,000,000								$ 27,000,000