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Retirement Benefits | 3 Months Ended
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Mar. 31, 2020
Retirement Benefits [Abstract] |
Retirement Benefits | Retirement Benefits The components of the net periodic pension benefit credit for the three months ended March 31 were as follows:
|  |  |  |  |  |  | 2020 |  | 2019
|  |  |  |  |  |  | (Dollars in thousands) |  |
Service cost |  |  |  |  |  |  | $ | 3,486 |  |  | $ | 3,258 |
Interest cost |  |  |  |  |  |  | 5,710 |  |  | 7,049 |
Expected return on plan assets |  |  |  |  |  |  | (17,993) |  |  | (15,113) |
Amortization of prior service cost |  |  |  |  |  |  | 55 |  |  | 19 |
Amortization of actuarial losses |  |  |  |  |  |  | 2,934 |  |  | 4,119 |
Net periodic benefit credit |  |  |  |  |  |  | $ | (5,808) |  |  | $ | (668) |
The components of the net periodic other postretirement benefit credit for the three months ended March 31 were as follows:
|  |  |  |  |  |  | 2020 |  | 2019
|  |  |  |  |  |  | (Dollars in thousands) |  |
Service cost |  |  |  |  |  |  | $ | 23 |  |  | $ | 22 |
Interest cost |  |  |  |  |  |  | 142 |  |  | 185 |
Amortization of prior service credit |  |  |  |  |  |  | (483) |  |  | (582) |
Amortization of actuarial gains |  |  |  |  |  |  | (70) |  |  | (167) |
Net periodic benefit credit |  |  |  |  |  |  | $ | (388) |  |  | $ | (542) |

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- References No definition available. + Details
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- Definition The entire disclosure for pension and other postretirement benefits. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -URI http://asc.fasb.org/topic&trid=2235017 + Details
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