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Employee Retirement Benefits - Net Periodic Income (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Pension Benefits [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets, Net of Management Fees | 7.35% | 7.35% |
Net periodic benefit (income) cost [Abstract] |  |  |
Service cost | $ 66 | $ 62 | $ 70
Interest cost | 83 | 105 | 97
Expected return on plan assets | (270) | (260) | (253)
Amortization of prior service cost (benefit) | (1) | 1 | 1
Amortization of losses | 0 | 0 | 0
Special termination benefits | 38 | 0 | 0
Postretirement benefits settlement | 0 | 0 | 0
Net periodic (income) cost | (84) | (92) | (85)
Other Benefits [Member] |  |  |
Net periodic benefit (income) cost [Abstract] |  |  |
Service cost | 1 | 2 | 3
Interest cost | 8 | 13 | 13
Expected return on plan assets | 0 | (1) | (1)
Amortization of prior service cost (benefit) | (10) | (2) | (3)
Amortization of losses | 0 | 0 | 2
Special termination benefits | 0 | 0 | 0
Postretirement benefits settlement | 1 | 0 | 0
Net periodic (income) cost | 0 | 12 | 14
FPL[Member] | Pension Benefits [Member] |  |  |
Net periodic benefit (income) cost [Abstract] |  |  |
Net periodic (income) cost | (51) | (58) | (55)
FPL[Member] | Other Benefits [Member] |  |  |
Net periodic benefit (income) cost [Abstract] |  |  |
Net periodic (income) cost | $ 0 | $ 9 | $ 11

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- Definition Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets, Net of Management Fees + References No definition available. + Details
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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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + 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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(5) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + 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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + 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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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