v3.26.1
Form 5500, Schedule H, Par IV, Line 4i - Schedule of assets [Held at End of Year] (Details) - EBP 001 - USD ($)
Dec. 31, 2025
Dec. 31, 2024
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 1,491,613,535  
Notes receivable from participants 10,852,946 $ 10,079,288
Investment, Identifier [Axis]: Common/Collective Trusts, BlackRock Total Return Bond Fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 106,882,055  
Number of shares (in shares) 9,358,474  
Investment, Identifier [Axis]: Common/Collective Trusts, Earnest Partners Smid Cap Core Fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 35,385,511  
Number of shares (in shares) 2,016,268  
Investment, Identifier [Axis]: Common/Collective Trusts, JPMCB Intermediate Bond Fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 50,937,832  
Number of shares (in shares) 2,590,938  
Investment, Identifier [Axis]: Common/Collective Trusts, JPMCB Intermediate Income Bond Fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 17,017,170  
Number of shares (in shares) 1,362,464  
Investment, Identifier [Axis]: Common/Collective Trusts, Northern Trust Collective Extended Equity Market Index Fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 125,013,455  
Number of shares (in shares) 86,068  
Investment, Identifier [Axis]: Common/Collective Trusts, State Street Global All Cap Equity Ex-U.S. Index Securities Lending Series Fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 92,649,356  
Number of shares (in shares) 4,990,001  
Investment, Identifier [Axis]: Common/Collective Trusts, State Street S&P 500 Index Securities Lending Series Fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 343,445,893  
Number of shares (in shares) 11,259,783  
Investment, Identifier [Axis]: Common/Collective Trusts, State Street U.S. Bond Index Securities Lending Series Fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 99,689,013  
Number of shares (in shares) 8,638,563  
Investment, Identifier [Axis]: Common/Collective Trusts, Winslow Large Cap Growth Fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 201,658,866  
Number of shares (in shares) 1,190,219  
Investment, Identifier [Axis]: Corporate Stocks: Common, Alliant Energy Corporation Common Stock    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 101,433,825  
Number of shares (in shares) 1,560,280  
Investment, Identifier [Axis]: Participant-Directed Brokerage Accounts, Self-Managed Brokerage Accounts    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 20,884,590  
Investment, Identifier [Axis]: Registered Investment Companies, American Funds EuroPacific Growth Fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 138,670,657  
Number of shares (in shares) 2,289,050  
Investment, Identifier [Axis]: Registered Investment Companies, Dodge & Cox Stock Fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 140,696,231  
Number of shares (in shares) 8,480,785  
Investment, Identifier [Axis]: Registered Investment Companies, Fidelity Investments Money Market Government Portfolio    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 2,455,324  
Number of shares (in shares) 2,455,324  
Investment, Identifier [Axis]: Registered Investment Companies, Vanguard Short-Term Inflation-Protected Securities Index Fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
Current Value $ 3,940,811  
Number of shares (in shares) 158,904