Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	480,000,000	480,000,000
Common stock, shares outstanding (in shares)	237,394,409	236,063,279
Shares in deferred compensation trust (in shares)	375,542	384,580
Shares in deferred compensation trust, weighted average cost per share (in dollars per share)	$ 25.93	$ 25.60
IPL [Member]
Common stock, par value	$ 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	$ 5.00	$ 5.00
Common stock, shares authorized (in shares)	18,000,000	18,000,000
Common stock, shares outstanding (in shares)	13,236,601	13,236,601