UNIT-BASED COMPENSATION Narrative 3 (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Restricted Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total fair value of restricted units that vested during the period	$ 6.5	$ 9.0
Units issued to satisfy award vestings, net of tax (units)	152,017
Unrecognized compensation cost	$ 25.5
Compensation cost not yet recognized, period for recognition	3 years 8 months 12 days
Restricted units, domestic employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unit-based compensation, vesting period	5 years
Unit-based awards, granted (units)	307,009	246,070
Unit-based awards, forfeited (units)	16,137	4,530
Restricted units, non-employee directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unit-based compensation, vesting period	3 years
Unit-based awards, granted (units)	17,110	8,730
Unit-based awards, forfeited (units)	0	0
Restricted units, international employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unit-based awards, granted (units)	24,533	20,107
Unit-based awards, forfeited (units)	595	3,807
Restricted units, international employees [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unit-based compensation, vesting period	3 years
Restricted units, international employees [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unit-based compensation, vesting period	5 years
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units issued to satisfy award vestings, net of tax (units)	33,438
Unit-based compensation, description of performance units	The objective performance measure is determined each year by the NuStar GP, LLC Compensation Committee for the following year. Achievement of the performance measure determines the rate at which the performance units convert into our common units, which can range from zero to 200%.
Unit-based compensation, terms of performance units	Performance units vest in three annual increments (tranches), based upon our achievement of the performance measure set by the Compensation Committee during the one-year performance periods that end on December 31 of each year following the date of grant.
Unit-based awards, granted (units)	38,865	0
Unit-based awards, forfeited (units)		0

Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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General descriptive information regarding an arrangement under which employees and directors receive: (a) awards of equity shares, equity share options, or other equity instruments; or (b) the entity incurs liabilities to them: (1) in amounts based, at least in part, on the price of the entity's shares or other equity instruments; or (2) that require or may require settlement by issuance of the entity's shares. Such an arrangement is usually provided to employees and directors to compensate them, provide performance incentives to them, and to attract or retain their services. May also include pertinent information particular to a plan that is not elsewhere specified in the taxonomy.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Description of pertinent provisions of equity-based compensation awards that have actual or potential impact upon the company's financial statements.

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Number of shares (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of any shares forfeited. Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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