Overview and Summary of Significant Accounting Policies - Unsatisfied Performance Obligation (Details) $ in Millions	Jun. 30, 2019 USD ($)
Energy Equipment Group | Wind towers and utility structures
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Unsatisfied performance obligations, Amount	$ 517.6
Unsatisfied performance obligations, Percent expected to be delivered in 2019	52.00%
Energy Equipment Group | Other
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Unsatisfied performance obligations, Amount	$ 45.3
Unsatisfied performance obligations, Percent expected to be delivered in 2019	80.00%
Transportation Products Group | Inland barge
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Unsatisfied performance obligations, Amount	$ 349.7
Unsatisfied performance obligations, Percent expected to be delivered in 2019	54.00%