Summary Of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2019 customer MW
General:
Electric capacity of wind farm (in megawatts)	1,000
IPL [Member]
General:
Generation and distribution of steam, number of customers served (in customers) | customer	2
Property, Plant and Equipment:
AFUDC accrual recorded, percentage of estimated CWIP	100.00%
WPL [Member]
Property, Plant and Equipment:
AFUDC accrual recorded, percentage of estimated CWIP	50.00%
AFUDC rates, projects with approval	100.00%
Alliant Energy Finance, LLC [Member]
General:
Ownership interest	50.00%
Electric capacity of wind farm (in megawatts)	225
Sheboygan Falls Energy Facility [Member]
General:
Fossil-fueled EGU capacity (in megawatts)	347
Finance lease, lease term	20 years