Related Party Transactions (Details) $ in Millions |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2018
USD ($)
item
|
Dec. 31, 2017
USD ($)
|
Dec. 31, 2016
USD ($)
|
|
Related party transactions | |||
Expenses incurred with related party | $ 3.2 | $ 3.2 | $ 3.2 |
Chairman and Chief Executive Officer | |||
Related party transactions | |||
Lease payment to related party | $ 3.0 | 2.8 | 2.8 |
O&G [Member] | |||
Related party transactions | |||
Ownership percentage in joint venture | 75.00% | ||
Related party's ownership percentage in joint venture | 25.00% | ||
O&G [Member] | Project In Los Angeles, California [Member] | |||
Related party transactions | |||
Number of construction projects | item | 1 | ||
Alliant [Member] | |||
Related party transactions | |||
Insurance expense | $ 14.7 | 17.6 | $ 8.9 |
Owed to related party | $ 4.1 | $ 0.5 |