Common Equity (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Common Equity [Line Items]
Other comprehensive income	$ 0	$ 0	$ 0	$ 0
IPL [Member]
Common Equity [Line Items]
Retained earnings free of dividend restrictions	553,000,000		553,000,000
Restricted net assets of subsidiaries	1,300,000,000		1,300,000,000
Capital contributions from parent			90,000,000	90,000,000
Common stock dividends to parent			105,000,000
Other comprehensive income	0	0	0	0
WPL [Member]
Common Equity [Line Items]
Retained earnings free of dividend restrictions	30,000,000		30,000,000
Restricted net assets of subsidiaries	1,700,000,000		1,700,000,000
Common stock dividends to parent			89,100,000
Other comprehensive income	$ 0	$ 0	$ 0	$ 0