Basis of Presentation and Summary of Significant Accounting Policies (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Earnings (Loss) Per Common Unit
Net income	$ 20,085us-gaap_IncomeLossAttributableToParent	$ 6,939us-gaap_IncomeLossAttributableToParent
Less: General partner incentive distribution rights	(3,887)	(2,518)
Less: General partner 2% ownership interest	(322)	(86)
General partner units, interest (as a percent)	2.00%exlp_GeneralPartnerUnitsInterest	2.00%exlp_GeneralPartnerUnitsInterest	2.00%exlp_GeneralPartnerUnitsInterest
Common units interest in net income	15,876	4,335
Less: Net income attributable to participating securities	(48)	(49)
Net income used in basic and diluted earnings per common unit	15,828	4,286
Adjustments to net income attributable to common unitholders for the diluted earnings per common unit calculation	$ 0us-gaap_DilutiveSecurities	$ 0us-gaap_DilutiveSecurities
Potential common units included in computing the dilutive potential common units used in dilutive earnings per common unit
Weighted average common units outstanding including participating securities (in units)	55,739	49,494
Less: Weighted average participating securities outstanding (in units)	(61)	(65)
Weighted average common units outstanding - used in basic earnings per common unit (in units)	55,678	49,429
Net dilutive potential common units issuable:
Phantom units (in units)		6
Weighted average common units and dilutive potential common units - used in diluted earnings per common unit (in units)	55,678	49,435

The general partner's interest in general partner units as a percentage of total units.

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Aggregate amount of net income allocated to general partners based on incentive distribution rights.

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Aggregate amount of net income allocated to general partners based on ownership interest.

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The amount of net income allocated to limited partners excluding net income attributable to participating securities which is used to calculate basic and diluted earnings per unit.

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Weighted average number of limited partnership units outstanding determined by relating the portion of time within a reporting period that limited partnership units have been outstanding to the total time in that period and weighted average participating securities outstanding during the period.

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Represents weighted average participating securities outstanding during the period.

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Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise stock options, restrictive stock units (RSUs), convertible preferred stock of an employee stock ownership plan (ESOP), and other dilutive convertible securities.

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The portion of profit or loss for the period which is attributable to the parent.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.20)

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 50

-Paragraph 1

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Aggregate amount of net income allocated to limited partners.

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Amount of earnings (loss) distributed and earnings (loss) allocated to participating securities for the basic earnings (loss) per share or per unit calculation under the two-class method.

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-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 45

-Paragraph 60B

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-Name Accounting Standards Codification

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-SubTopic 10

-Section S99

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-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187171-122770

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-Name Staff Accounting Bulletin (SAB)

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-Section F

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Weighted average number of limited partnership units outstanding determined by relating the portion of time within a reporting period that limited partnership units have been outstanding to the total time in that period. Used in the calculation of diluted net income or loss per limited partnership unit.

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