Subsequent events (Details) - Natural Gas Processing Plant - Subsequent Event - Effingham County Power $ in Millions	Jul. 08, 2021 USD ($) MW
Subsequent Event [Line Items]
Generating capacity of each nuclear unit \| MW	511
Purchase price \| $	$ 232.5

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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