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Benefit Plans (Narrative) (Details) $ / shares in Units, $ in Millions | 6 Months Ended
--- | ---
Jun. 30, 2019 USD ($) $ / shares shares
Defined Benefit Plan Disclosure [Line Items] |
Unrecognized compensation cost | $ | $ 10.3
Minimum [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Unrecognized compensation cost recognized over a weighted average period | 1 year
Maximum [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Unrecognized compensation cost recognized over a weighted average period | 2 years
IPL [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Unrecognized compensation cost | $ | $ 5.7
WPL [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Unrecognized compensation cost | $ | $ 4.2
Performance Shares [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Performance period | 3 years
Granted (in shares/awards) | 80,837
Granted, weighted average grant date fair value (in dollars per share) | $ / shares | $ 46.35
Performance Shares [Member] | Minimum [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Actual number of shares paid out upon vesting, percentage of target shares | 0.00%
Performance Shares [Member] | Maximum [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Actual number of shares paid out upon vesting, percentage of target shares | 200.00%
Performance Restricted Stock Unit [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Performance period | 3 years
Granted (in shares/awards) | 80,837
Granted, weighted average grant date fair value (in dollars per share) | $ / shares | $ 45.63
Instrument valuation based on shares of common stock, number of shares | 1
Performance Restricted Stock Unit [Member] | Minimum [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Actual number of shares paid out upon vesting, percentage of target shares | 0.00%
Performance Restricted Stock Unit [Member] | Maximum [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Actual number of shares paid out upon vesting, percentage of target shares | 200.00%
Restricted Stock Units [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Performance period | 3 years
Granted (in shares/awards) | 95,938
Granted, weighted average grant date fair value (in dollars per share) | $ / shares | $ 45.63
Instrument valuation based on shares of common stock, number of shares | 1

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- Definition Amount of cost not yet recognized for nonvested award under share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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