Commitments And Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Long-term Purchase Commitment [Line Items]
Minimum future commitments	$ 2,423
Performance guarantees outstanding	313
Present value abandonment obligation	31
IPL [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	1,902
Number of sites monitoring and remediating (in sites)	27
WPL [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	518
Number of sites monitoring and remediating (in sites)	5
Capital Purchase Obligation [Member] | Alliant Energy and IPL [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	59
Indemnification Agreement [Member] | RMT [Member]
Long-term Purchase Commitment [Line Items]
Loss contingency, estimate of possible loss	3
Performance guarantees outstanding, 2014 [Member]
Long-term Purchase Commitment [Line Items]
Performance guarantees outstanding	137
Performance guarantees outstanding, 2015 [Member]
Long-term Purchase Commitment [Line Items]
Performance guarantees outstanding	53
Performance guarantees outstanding, 2016 [Member]
Long-term Purchase Commitment [Line Items]
Performance guarantees outstanding	123
Environmental Issue [Member] | WPL [Member]
Long-term Purchase Commitment [Line Items]
Loss contingency, damages awarded, value	$ 7
Minimum [Member]
Long-term Purchase Commitment [Line Items]
Warranty period	12 months
Maximum [Member]
Long-term Purchase Commitment [Line Items]
Warranty period	60 months