Common Equity (Narrative) (Details) (USD $)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
IPL [Member]
Common Equity [Line Items]
Retained earnings free of dividend restrictions	$ 485,000,000
Restricted net assets of subsidiaries	1,200,000,000
Capital contributions from parent	60,000,000	60,000,000
Common stock dividends to parent	70,000,000
WPL [Member]
Common Equity [Line Items]
Retained earnings free of dividend restrictions	59,000,000
Restricted net assets of subsidiaries	1,600,000,000
Common stock dividends to parent	$ 59,400,000