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Retirement Benefits (Schedule Of Net Benefit Costs) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
DB Pension Plans |  |  |  |
Net periodic cost (credit) |  |  |  |
Service cost | $ 11 | $ 12 | $ 31 | $ 36
Interest cost | 24 | 22 | 73 | 67
Expected return on plan assets | (40) | (38) | (121) | (112)
Amortization of: |  |  |  |
Net loss | 12 | 19 | 36 | 56
Prior service cost (credit) | 0 | 1 | 1 | 2
Net periodic cost (credit) | 7 | 16 | 20 | 49
DB Pension Plans | Consumers Energy Company |  |  |  |
Net periodic cost (credit) |  |  |  |
Service cost | 10 | 12 | 30 | 35
Interest cost | 23 | 22 | 69 | 64
Expected return on plan assets | (38) | (35) | (114) | (104)
Amortization of: |  |  |  |
Net loss | 12 | 17 | 35 | 53
Prior service cost (credit) | 0 | 1 | 1 | 2
Net periodic cost (credit) | 7 | 17 | 21 | 50
OPEB Plan |  |  |  |
Net periodic cost (credit) |  |  |  |
Service cost | 3 | 4 | 10 | 13
Interest cost | 11 | 9 | 31 | 27
Expected return on plan assets | (22) | (24) | (66) | (73)
Amortization of: |  |  |  |
Net loss | 7 | 3 | 20 | 11
Prior service cost (credit) | (16) | (16) | (47) | (50)
Net periodic cost (credit) | (17) | (24) | (52) | (72)
OPEB Plan | Consumers Energy Company |  |  |  |
Net periodic cost (credit) |  |  |  |
Service cost | 3 | 4 | 10 | 12
Interest cost | 10 | 8 | 30 | 25
Expected return on plan assets | (21) | (22) | (62) | (68)
Amortization of: |  |  |  |
Net loss | 7 | 4 | 20 | 12
Prior service cost (credit) | (15) | (17) | (46) | (49)
Net periodic cost (credit) | $ (16) | $ (23) | $ (48) | $ (68)

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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 cost for actuarial present value of benefits attributed to service rendered by employee for 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)(1) -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)(1) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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