Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Name:	us-gaap_RegulatoryLiabilitiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Regulatory Matters (Customer Billing Credits) (Details) - IPL [Member] - USD ($) $ in Millions	12 Months Ended			36 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Regulatory Liabilities [Line Items]
Billing credits to reduce retail electric customers' bills		$ 24	$ 72
Scenario, Forecast [Member]
Regulatory Liabilities [Line Items]
Billing credits to reduce retail electric customers' bills	$ 9			$ 105