Summary of Significant Accounting Policies - Investments in Affiliates and Other Entities (Details) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020 USD ($) mile	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2014 substation kV km
Summary Of Significant Accounting Policies [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	$ (4,784)		$ 1,757		$ (7,467)	$ 62,147
Impairment of cost method investment	$ 9,311		$ 0		9,311	$ 0
EPC Electric Transmission Project
Summary Of Significant Accounting Policies [Line Items]
Length of electrical transmission line to be constructed under contract | km							500
Number of substations | substation							2
Voltage of substations | kV							500
Deferred earnings recognized				$ 60,300
Gain related to the sale of interest in limited partnership		$ 13,000
LUMA Energy, LLC
Summary Of Significant Accounting Policies [Line Items]
Term of operation and maintenance agreement	15 years
Length of electric transmission and distribution system | mile	18,000
Transition period	1 year
Certain Non-Integral Equity Investments
Summary Of Significant Accounting Policies [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	$ (5,500)				$ (8,700)
LUMA Energy, LLC
Summary Of Significant Accounting Policies [Line Items]
Equity interest	50.00%				50.00%
Investment balance	$ 600				$ 600
Infrastructure Investors Partnership
Summary Of Significant Accounting Policies [Line Items]
Investment balance	23,900				$ 23,900
Water and Gas Pipeline Infrastructure Contractor
Summary Of Significant Accounting Policies [Line Items]
Equity interest acquired					30.00%
Investment balance	$ 11,400				$ 11,400
Remaining equity interest which the company has an option to acquire	70.00%
Impairment of cost method investment	$ 9,300