Regulatory Environment - NSG 2021 Rate Order (Details) - Illinois Commerce Commission (ICC) - 2021 Rate order - NSG $ in Millions	1 Months Ended
	Sep. 30, 2021 USD ($)
Public Utilities, General Disclosures
Approved rate increase	$ 4.1
Approved rate increase (as a percent)	4.50%
Approved return on equity (as a percent)	9.67%
Approved common equity component average (as a percent)	51.58%