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Retirement Benefits (Schedule Of Net Benefit Costs) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018
DB Pension Plans |  |  |  |
Net periodic cost (credit) |  |  |  |
Service cost | $ 10 | $ 12 | $ 20 | $ 24
Interest cost | 24 | 23 | 49 | 45
Expected return on plan assets | (41) | (37) | (81) | (74)
Amortization of: |  |  |  |
Net loss | 12 | 19 | 24 | 37
Prior service cost (credit) | 1 | 0 | 1 | 1
Net periodic cost (credit) | 6 | 17 | 13 | 33
DB Pension Plans | Consumers Energy Company |  |  |  |
Net periodic cost (credit) |  |  |  |
Service cost | 10 | 11 | 20 | 23
Interest cost | 23 | 21 | 46 | 42
Expected return on plan assets | (38) | (34) | (76) | (69)
Amortization of: |  |  |  |
Net loss | 11 | 18 | 23 | 36
Prior service cost (credit) | 1 | 0 | 1 | 1
Net periodic cost (credit) | 7 | 16 | 14 | 33
OPEB Plan |  |  |  |
Net periodic cost (credit) |  |  |  |
Service cost | 3 | 5 | 7 | 9
Interest cost | 10 | 9 | 20 | 18
Expected return on plan assets | (22) | (25) | (44) | (49)
Amortization of: |  |  |  |
Net loss | 6 | 4 | 13 | 8
Prior service cost (credit) | (15) | (17) | (31) | (34)
Net periodic cost (credit) | (18) | (24) | (35) | (48)
OPEB Plan | Consumers Energy Company |  |  |  |
Net periodic cost (credit) |  |  |  |
Service cost | 4 | 4 | 7 | 8
Interest cost | 10 | 9 | 20 | 17
Expected return on plan assets | (20) | (23) | (41) | (46)
Amortization of: |  |  |  |
Net loss | 6 | 4 | 13 | 8
Prior service cost (credit) | (16) | (16) | (31) | (32)
Net periodic cost (credit) | $ (16) | $ (22) | $ (32) | $ (45)

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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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