v3.10.0.1

EMPLOYEE BENEFIT PLANS | 6 Months Ended
--- | ---
Jun. 30, 2018
Retirement Benefits [Abstract] |
EMPLOYEE BENEFIT PLANS | EMPLOYEE BENEFIT PLANS NuStar’s Pension Plan is a qualified non-contributory defined benefit pension plan that provides eligible U.S. employees with retirement income as calculated under a cash balance formula. NuStar’s Excess Pension Plan is a nonqualified deferred compensation plan that provides benefits to a select group of management or other highly compensated employees. The Pension Plan and Excess Pension Plan are collectively referred to as the Pension Plans. We also sponsor a contributory medical benefits plan for U.S. employees who retired prior to April 1, 2014. For employees who retire on or after April 1, 2014, we provide partial reimbursement for eligible third-party health care premiums. The components of net periodic benefit cost (income) related to our Pension Plans and other postretirement benefit plans were as follows:
| Pension Plans |  | Other Postretirement Benefit Plans
| 2018 |  | 2017 |  | 2018 |  | 2017
| (Thousands of Dollars)
For the three months ended June 30: |  |  |  |  |  |  |
Service cost | $ | 2,405 |  |  | $ | 2,239 |  |  | $ | 126 |  |  | $ | 113 |
Interest cost | 1,206 |  |  | 1,127 |  |  | 107 |  |  | 108 |
Expected return on assets | (1,854 | ) |  | (1,602 | ) |  | — |  |  | — |
Amortization of prior service credit | (514 | ) |  | (516 | ) |  | (286 | ) |  | (286 | )
Amortization of net loss | 543 |  |  | 371 |  |  | 53 |  |  | 48 |
Net periodic benefit cost (income) | $ | 1,786 |  |  | $ | 1,619 |  |  | $ | — |  |  | $ | (17 | )
For the six months ended June 30: |  |  |  |  |  |  |
Service cost | $ | 4,811 |  |  | $ | 4,478 |  |  | $ | 252 |  |  | $ | 226 |
Interest cost | 2,412 |  |  | 2,254 |  |  | 215 |  |  | 216 |
Expected return on assets | (3,709 | ) |  | (3,205 | ) |  | — |  |  | — |
Amortization of prior service credit | (1,028 | ) |  | (1,031 | ) |  | (573 | ) |  | (572 | )
Amortization of net loss | 1,087 |  |  | 742 |  |  | 107 |  |  | 96 |
Net periodic benefit cost (income) | $ | 3,573 |  |  | $ | 3,238 |  |  | $ | 1 |  |  | $ | (34 | )

X
- References No definition available. + Details
Name: | us-gaap_CompensationAndRetirementDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The entire disclosure for pension and other postretirement benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -URI http://asc.fasb.org/topic&trid=2235017 + Details
Name: | us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration