Commitments And Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 2,283
Performance guarantees outstanding	251
Present value abandonment obligation	35
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	1,795
Number of sites monitoring and remediating (in sites)	25
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	488
Number of sites monitoring and remediating (in sites)	5
Capital Purchase Obligation [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	26
Capital Purchase Obligation [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	2
Capital Purchase Obligation [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	24
Performance guarantees outstanding, 2015 [Member]
Commitments and Contingencies [Line Items]
Performance guarantees outstanding	128
Performance guarantees outstanding, 2016 [Member]
Commitments and Contingencies [Line Items]
Performance guarantees outstanding	48
Performance guarantees outstanding, 2017 [Member]
Commitments and Contingencies [Line Items]
Performance guarantees outstanding	75
Environmental Issue [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Environmental mitigation projects to be completed, value	$ 7
Minimum [Member]
Commitments and Contingencies [Line Items]
Warranty period	12 months
Maximum [Member]
Commitments and Contingencies [Line Items]
Warranty period	60 months