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EMPLOYEE BENEFITS (Tables) | 3 Months Ended
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Mar. 31, 2018
Retirement Benefits [Abstract] |
Schedule of Net Benefit Costs | The following tables show the components of net periodic pension and OPEB costs for our benefit plans.
|  | Pension Costs
|  | Three Months Ended March 31
(in millions) |  | 2018 |  | 2017
Service cost |  | $ | 12.0 |  |  | $ | 11.7 |
Interest cost |  | 28.3 |  |  | 31.2 |
Expected return on plan assets |  | (49.6 | ) |  | (49.6 | )
Loss on plan settlement |  | 0.4 |  |  | — |
Amortization of prior service cost |  | 0.7 |  |  | 0.7 |
Amortization of net actuarial loss |  | 23.1 |  |  | 21.9 |
Net periodic benefit cost |  | $ | 14.9 |  |  | $ | 15.9 |
|  | OPEB Costs
|  | Three Months Ended March 31
(in millions) |  | 2018 |  | 2017
Service cost |  | $ | 6.2 |  |  | $ | 6.3 |
Interest cost |  | 7.5 |  |  | 8.5 |
Expected return on plan assets |  | (14.9 | ) |  | (13.7 | )
Amortization of prior service credit |  | (3.8 | ) |  | (2.8 | )
Amortization of net actuarial loss |  | 0.3 |  |  | 1.5 |
Net periodic benefit credit |  | $ | (4.7 | ) |  | $ | (0.2 | )
Schedule of retroactively restated Income Statement | The impacts to our income statements from adoption of this standard are reflected in the table below.
|  | Year Ended December 31, 2017 |  | Year Ended December 31, 2016 |  | Year Ended December 31, 2015
(in millions) |  | Form 10-K Income Statement |  | Impact of ASU 2017-07 |  | Income Statement After Adoption |  | Form 10-K Income Statement |  | Impact of ASU 2017-07 |  | Income Statement After Adoption |  | Form 10-K Income Statement |  | Impact of ASU 2017-07 |  | Income Statement After Adoption
Operating expenses |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other operation and maintenance |  | $ | 2,047.0 |  |  | $ | 9.1 |  |  | $ | 2,056.1 |  |  | $ | 2,185.5 |  |  | $ | (14.2 | ) |  | $ | 2,171.3 |  |  | $ | 1,709.3 |  |  | $ | 1.4 |  |  | $ | 1,710.7 |
Other expense |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other income, net |  | 64.6 |  |  | 9.1 |  |  | 73.7 |  |  | 80.8 |  |  | (14.2 | ) |  | 66.6 |  |  | 58.9 |  |  | 1.4 |  |  | 60.3 |

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- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. + 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) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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