Revenue (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenue From Contract With Customer [Line Items]
Revenue, remaining performance obligation	$ 474,895
Percentage of performance obligation to be recognized as revenue	90.00%
Performance obligation, expected to be recognized as revenue year	2020
Remaining performance obligation, expected timing of satisfaction, year	2021
Amortization on pre-construction costs	$ 5,191	$ 2,751
Other Current and Noncurrent Assets [Member]
Revenue From Contract With Customer [Line Items]
Costs to fulfill a contract with customer recognized as an asset	$ 8,570		$ 10,300