Income Taxes (Schedule Of Components Of Income Tax) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current tax expense (benefit):
Federal	$ (6.6)	$ (1.0)	$ (41.0)
State	24.2	(5.1)	8.5
Deferred tax expense (benefit):
Federal	69.7	67.9	159.5
State	41.4	29.8	12.3
Production tax credits	(54.7)	(29.5)	(31.1)
Investment tax credits	(0.8)	(1.2)	(1.1)
Income tax expense (benefit)	68.7	47.7	66.7
IPL's tax benefit riders [Member]
Current tax expense (benefit):
IPL's tax benefit riders	(4.5)	(13.2)	(40.4)
IPL [Member]
Current tax expense (benefit):
Federal	(11.0)	14.9	(27.9)
State	24.3	(7.1)	1.6
Deferred tax expense (benefit):
Federal	26.4	9.5	72.5
State	30.9	7.3	(2.2)
Production tax credits	(41.8)	(14.0)	(14.1)
Investment tax credits	(0.2)	(0.6)	(0.4)
Income tax expense (benefit)	24.1	(3.2)	(10.9)
IPL [Member] | IPL's tax benefit riders [Member]
Current tax expense (benefit):
IPL's tax benefit riders	(4.5)	(13.2)	(40.4)
WPL [Member]
Current tax expense (benefit):
Federal	12.0	(9.2)	5.5
State	13.7	(4.4)	2.5
Deferred tax expense (benefit):
Federal	30.7	43.8	55.0
State	6.3	22.1	16.6
Production tax credits	(12.8)	(15.5)	(17.0)
Investment tax credits	(0.6)	(0.6)	(0.7)
Income tax expense (benefit)	$ 49.3	$ 36.2	$ 61.9