Commitments And Contingencies (Operating Expense Purchase Obligations) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Long-term Purchase Commitment [Line Items]
Minimum future commitments	$ 2,400
Individual commitments incurred	1
Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	1,418	[1]
Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	771
Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	177	[2]
Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	34	[3]
2017 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	529
2017 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	185	[1]
2017 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	223
2017 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	105	[2]
2017 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	16	[3]
2018 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	389
2018 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	189	[1]
2018 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	142
2018 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	54	[2]
2018 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	4	[3]
2019 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	297
2019 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	159	[1]
2019 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	115
2019 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	18	[2]
2019 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	5	[3]
2020 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	237
2020 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	137	[1]
2020 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	98
2020 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[2]
2020 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	2	[3]
2021 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	220
2021 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	149	[1]
2021 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	69
2021 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[2]
2021 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	2	[3]
Thereafter [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	728
Thereafter [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	599	[1]
Thereafter [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	124
Thereafter [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[2]
Thereafter [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	5	[3]
IPL [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	1,774
IPL [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	1,298	[1]
IPL [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	382
IPL [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	77	[2]
IPL [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	17	[3]
IPL [Member] | 2017 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	322
IPL [Member] | 2017 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	138	[1]
IPL [Member] | 2017 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	120
IPL [Member] | 2017 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	49	[2]
IPL [Member] | 2017 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	15	[3]
IPL [Member] | 2018 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	225
IPL [Member] | 2018 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	131	[1]
IPL [Member] | 2018 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	74
IPL [Member] | 2018 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	19	[2]
IPL [Member] | 2018 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	1	[3]
IPL [Member] | 2019 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	209
IPL [Member] | 2019 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	144	[1]
IPL [Member] | 2019 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	55
IPL [Member] | 2019 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	9	[2]
IPL [Member] | 2019 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	1	[3]
IPL [Member] | 2020 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	176
IPL [Member] | 2020 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	137	[1]
IPL [Member] | 2020 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	39
IPL [Member] | 2020 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[2]
IPL [Member] | 2020 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[3]
IPL [Member] | 2021 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	172
IPL [Member] | 2021 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	149	[1]
IPL [Member] | 2021 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	23
IPL [Member] | 2021 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[2]
IPL [Member] | 2021 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[3]
IPL [Member] | Thereafter [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	670
IPL [Member] | Thereafter [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	599	[1]
IPL [Member] | Thereafter [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	71
IPL [Member] | Thereafter [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[2]
IPL [Member] | Thereafter [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[3]
WPL [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	611
WPL [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	120	[1]
WPL [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	389
WPL [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	100	[2]
WPL [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	2	[3]
WPL [Member] | 2017 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	206
WPL [Member] | 2017 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	47	[1]
WPL [Member] | 2017 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	103
WPL [Member] | 2017 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	56	[2]
WPL [Member] | 2017 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[3]
WPL [Member] | 2018 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	162
WPL [Member] | 2018 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	58	[1]
WPL [Member] | 2018 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	68
WPL [Member] | 2018 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	35	[2]
WPL [Member] | 2018 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	1	[3]
WPL [Member] | 2019 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	85
WPL [Member] | 2019 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	15	[1]
WPL [Member] | 2019 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	60
WPL [Member] | 2019 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	9	[2]
WPL [Member] | 2019 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	1	[3]
WPL [Member] | 2020 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	59
WPL [Member] | 2020 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[1]
WPL [Member] | 2020 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	59
WPL [Member] | 2020 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[2]
WPL [Member] | 2020 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[3]
WPL [Member] | 2021 [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	46
WPL [Member] | 2021 [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[1]
WPL [Member] | 2021 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	46
WPL [Member] | 2021 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[2]
WPL [Member] | 2021 [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[3]
WPL [Member] | Thereafter [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	53
WPL [Member] | Thereafter [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[1]
WPL [Member] | Thereafter [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	53
WPL [Member] | Thereafter [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	0	[2]
WPL [Member] | Thereafter [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	$ 0	[3]

[1] Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased.

[2] Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of December 31, 2016 regarding expected future usage, which is subject to change.

[3] Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2016.