Commitments and Contingencies (Investment Arrangements) (Narrative) (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Other Commitments [Line Items]
Cash	$ 59,176,000	$ 27,422,000	$ 20,684,000	$ 40,326,000
Other current liabilities	88,831,000	80,937,000
Proportionately Consolidated Non-Controlled Joint Venture [Member]
Other Commitments [Line Items]
Cash	29,600,000	11,800,000
Proportionately Consolidated Non-Controlled Joint Venture [Member] | Advances on Project Work [Member]
Other Commitments [Line Items]
Other current liabilities	$ 0	$ 7,000,000.0
Proportionately Consolidated Non-Controlled Joint Venture [Member] | Pacer [Member]
Other Commitments [Line Items]
Proportionately consolidated non-controlled joint venture, ownership percentage	35.00%
Proportionately Consolidated Non-Controlled Joint Venture [Member] | Joint Ventures That Provide Electrical Transmission Infrastructure Services [Member] | Minimum [Member]
Other Commitments [Line Items]
Proportionately consolidated non-controlled joint venture, ownership percentage	85.00%
Proportionately Consolidated Non-Controlled Joint Venture [Member] | Joint Ventures That Provide Electrical Transmission Infrastructure Services [Member] | Maximum [Member]
Other Commitments [Line Items]
Proportionately consolidated non-controlled joint venture, ownership percentage	90.00%