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Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Defined benefit pension plans [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost | $ 2.5 | $ 3.1 | $ 7.3 | $ 9.1
Interest cost | 12.5 | 11.7 | 37.4 | 35.1
Expected return on plan assets | (15.1) | (17.4) | (45.1) | (52.3)
Amortization of prior service credit | (0.2) | (0.2) | (0.5) | (0.5)
Amortization of actuarial loss | 9.1 | 8.8 | 27.3 | 26.4
Total | 8.8 | 6.0 | 26.4 | 17.8
OPEB Plans [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost | 0.8 | 1.0 | 2.5 | 3.1
Interest cost | 2.2 | 2.0 | 6.4 | 5.8
Expected return on plan assets | (1.2) | (1.5) | (3.7) | (4.5)
Amortization of prior service credit | (0.1) | 0.0 | (0.2) | (0.1)
Amortization of actuarial loss | 0.8 | 0.8 | 2.4 | 2.5
Total | 2.5 | 2.3 | 7.4 | 6.8
IPL [Member] | Defined benefit pension plans [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost | 1.6 | 1.8 | 4.6 | 5.5
Interest cost | 5.6 | 5.3 | 17.0 | 16.0
Expected return on plan assets | (7.0) | (8.1) | (21.1) | (24.4)
Amortization of prior service credit | (0.1) | 0.0 | (0.2) | (0.1)
Amortization of actuarial loss | 3.9 | 3.7 | 11.8 | 11.2
Total | 4.0 | 2.7 | 12.1 | 8.2
IPL [Member] | OPEB Plans [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost | 0.3 | 0.4 | 1.0 | 1.3
Interest cost | 0.8 | 0.7 | 2.5 | 2.3
Expected return on plan assets | (0.9) | (1.1) | (2.7) | (3.3)
Amortization of prior service credit | 0.0 | 0.0 | 0.0 | 0.0
Amortization of actuarial loss | 0.4 | 0.4 | 1.1 | 1.0
Total | 0.6 | 0.4 | 1.9 | 1.3
WPL [Member] | Defined benefit pension plans [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost | 0.9 | 1.1 | 2.6 | 3.3
Interest cost | 5.3 | 5.0 | 16.1 | 15.1
Expected return on plan assets | (6.5) | (7.6) | (19.6) | (22.8)
Amortization of prior service credit | 0.0 | 0.0 | (0.1) | (0.1)
Amortization of actuarial loss | 4.4 | 4.3 | 13.2 | 12.9
Total | 4.1 | 2.8 | 12.2 | 8.4
WPL [Member] | OPEB Plans [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost | 0.3 | 0.4 | 0.9 | 1.2
Interest cost | 0.9 | 0.8 | 2.6 | 2.3
Expected return on plan assets | (0.2) | (0.2) | (0.5) | (0.5)
Amortization of prior service credit | 0.0 | 0.0 | (0.1) | (0.1)
Amortization of actuarial loss | 0.4 | 0.5 | 1.2 | 1.5
Total | $ 1.4 | $ 1.5 | $ 4.1 | $ 4.4

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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details
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- Definition Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(5) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(5) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details
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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details
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- Definition Amount of cost recognized for passage of time related to defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details
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