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Pension Plans And Other Postretirement Benefit Plans (Tables) | 6 Months Ended
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Jun. 30, 2018
Components of Net Periodic Benefit Cost |
| Pension Benefits |  | Other Postretirement Benefits
| 2018 |  | 2017 |  | 2018 |  | 2017
Three months ended June 30: |  |  |  |  |  |  |
Service cost (a) | $ | 5,450 |  |  | $ | 5,092 |  |  | $ | 804 |  |  | $ | 799 |
Interest cost | 6,466 |  |  | 6,976 |  |  | 1,197 |  |  | 1,374 |
Expected return on plan assets | (8,250 | ) |  | (7,900 | ) |  | (500 | ) |  | (475 | )
Amortization of prior service cost | 75 |  |  | — |  |  | 209 |  |  | (312 | )
Net loss recognition | 1,842 |  |  | 2,317 |  |  | 562 |  |  | 1,320 |
Net periodic benefit cost | $ | 5,583 |  |  | $ | 6,485 |  |  | $ | 2,272 |  |  | $ | 2,706 |
Six months ended June 30: |  |  |  |  |  |  |
Service cost (a) | $ | 10,900 |  |  | $ | 10,134 |  |  | $ | 1,608 |  |  | $ | 1,623 |
Interest cost | 12,932 |  |  | 13,927 |  |  | 2,394 |  |  | 2,773 |
Expected return on plan assets | (16,500 | ) |  | (15,800 | ) |  | (1,000 | ) |  | (950 | )
Amortization of prior service cost | 150 |  |  | — |  |  | (606 | ) |  | (624 | )
Net loss recognition | 3,930 |  |  | 4,863 |  |  | 2,217 |  |  | 2,593 |
Net periodic benefit cost | $ | 11,412 |  |  | $ | 13,124 |  |  | $ | 4,613 |  |  | $ | 5,415 |
(a) | Total service costs in the table above are recorded to the same accounts as labor expense. Labor and benefits expense is recorded to various projects based on whether the work is a capital project or an operating expense. Approximately 40 percent of all labor and benefits is capitalized to utility property and 60 percent is expensed to utility other operating expenses.

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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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