Consolidated Balance Sheets (Parenthetical) - $ / shares		Dec. 31, 2016	Dec. 31, 2015
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	[1]	480,000,000	480,000,000
Common stock, shares outstanding (in shares)	[1]	227,673,654	226,918,432
Shares in deferred compensation trust (in shares)	[1]	441,695	430,186
Shares in deferred compensation trust, weighted average cost per share (in dollars per share)	[1]	$ 22.71	$ 19.84
IPL [Member]
Common stock, par value (in dollars per share)		$ 2.50	$ 2.50
Common stock, shares authorized (in shares)		24,000,000	24,000,000
Common stock, shares outstanding (in shares)		13,370,788	13,370,788
WPL [Member]
Common stock, par value (in dollars per share)		$ 5	$ 5
Common stock, shares authorized (in shares)		18,000,000	18,000,000
Common stock, shares outstanding (in shares)		13,236,601	13,236,601

[1] Amounts reflect the effects of a two-for-one common stock split distributed in May 2016.