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EMPLOYEE BENEFITS (Tables) | 6 Months Ended
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Jun. 30, 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 June 30 |  | Six Months Ended June 30
(in millions) |  | 2018 |  | 2017 |  | 2018 |  | 2017
Service cost |  | $ | 11.8 |  |  | $ | 10.4 |  |  | $ | 23.8 |  |  | $ | 22.1 |
Interest cost |  | 28.7 |  |  | 30.2 |  |  | 57.0 |  |  | 61.4 |
Expected return on plan assets |  | (48.8 | ) |  | (48.5 | ) |  | (98.4 | ) |  | (98.1 | )
Loss on plan settlement |  | 0.3 |  |  | 5.3 |  |  | 0.7 |  |  | 5.3 |
Amortization of prior service cost |  | 0.6 |  |  | 0.8 |  |  | 1.3 |  |  | 1.5 |
Amortization of net actuarial loss |  | 23.9 |  |  | 21.1 |  |  | 47.0 |  |  | 43.0 |
Net periodic benefit cost |  | $ | 16.5 |  |  | $ | 19.3 |  |  | $ | 31.4 |  |  | $ | 35.2 |
|  | OPEB Costs
|  | Three Months Ended June 30 |  | Six Months Ended June 30
(in millions) |  | 2018 |  | 2017 |  | 2018 |  | 2017
Service cost |  | $ | 5.6 |  |  | $ | 5.6 |  |  | $ | 11.8 |  |  | $ | 11.9 |
Interest cost |  | 7.4 |  |  | 8.4 |  |  | 14.9 |  |  | 16.9 |
Expected return on plan assets |  | (14.8 | ) |  | (13.6 | ) |  | (29.7 | ) |  | (27.3 | )
Amortization of prior service credit |  | (3.9 | ) |  | (2.8 | ) |  | (7.7 | ) |  | (5.6 | )
Amortization of net actuarial loss |  | 0.2 |  |  | 0.1 |  |  | 0.5 |  |  | 1.6 |
Net periodic benefit credit |  | $ | (5.5 | ) |  | $ | (2.3 | ) |  | $ | (10.2 | ) |  | $ | (2.5 | )
Schedule of non-service components | The following table shows the non-service credit components of net benefit costs:
|  | Three Months Ended June 30 |  | Six Months Ended June 30
(in millions) |  | 2018 |  | 2017 |  | 2018 |  | 2017
Non-service credit components |  | $ | (5.3 | ) |  | $ | — |  |  | $ | (12.5 | ) |  | $ | (2.6 | )

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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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