Document And Entity Information	9 Months Ended
	Sep. 30, 2018 shares
Entity Registrant Name	ALLIANT ENERGY CORP
Entity Central Index Key	0000352541
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	235,936,447
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
IPL [Member]
Entity Registrant Name	INTERSTATE POWER & LIGHT CO
Entity Central Index Key	0000052485
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding	13,370,788
WPL [Member]
Entity Registrant Name	WISCONSIN POWER & LIGHT CO
Entity Central Index Key	0000107832
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding	13,236,601