Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 161.8		$ 0.0
Money market fund investments interest rate, percentage	2.40%
Increase in operating cash flows from change in method of presentation to daily transactional activity		$ 339.4
Net cash flows from operating activities	$ 276.9	274.4
IPL [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in operating cash flows from change in method of presentation to daily transactional activity		339.4
Net cash flows from operating activities	89.0	12.8
WPL [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 160.4		$ 0.0
Money market fund investments interest rate, percentage	2.40%
Net cash flows from operating activities	$ 208.2	$ 225.9