Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Aggregate carrying value as of the balance sheet date of the liabilities for stock option plans and other equity-based compensation arrangements payable within one year (or the operating cycle, if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

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).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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UNIT-BASED COMPENSATION PLANS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
LTIP and Option Plan
Share-based Compensation Arrangement by Share-based Payment Award
Compensation expense	$ 8.2	$ 8.9	$ 25.9	$ 23.0
Long Term Incentive Plan 2013
Share-based Compensation Arrangement by Share-based Payment Award
LP Units, available for issuance (in shares)	2,646,326		2,646,326
Awards granted (in shares)			547,000
Long Term Incentive Plan 2013 \| Phantom Stock Units \| Employee
Share-based Compensation Arrangement by Share-based Payment Award
Awards granted (in shares)			316,490
Long Term Incentive Plan 2013 \| Phantom Stock Units \| Independent directors
Share-based Compensation Arrangement by Share-based Payment Award
Awards granted (in shares)			18,000
Long Term Incentive Plan 2013 \| Performance Shares \| Employee
Share-based Compensation Arrangement by Share-based Payment Award
Awards granted (in shares)			212,062
Long Term Incentive Plan 2009, Deferral Plan
Share-based Compensation Arrangement by Share-based Payment Award
Compensation awards deferred					$ 4.4	$ 3.1
Long Term Incentive Plan 2009, Deferral Plan \| Phantom Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Awards granted (in shares)			145,138		139,526