Long Term Debt (Credit Agreement) (Textual) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2013
Debt Disclosure [Abstract]
Line Of Credit Facility Initiation Date 1	Mar. 05, 2013
Line Of Credit Facility Expiration Date 1	Mar. 05, 2016
Line of Credit Facility, Maximum Borrowing Capacity	$ 75.0
Line Of Credit Facility Collateral Units	10,700,000
Line Of Credit Facility Base Interest Rate	5.00%
Line Of Credit Facility Unused Capacity Commitment Fee Percentage	0.75%
Line Of Credit Facility Loan To Equity Value Percentage	47.00%
Line Of Credit Facility Termination Fee	0.75%
Line Of Credit Facility Loan To Equity Value Percentage 1	42.50%

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Date the credit facility terminates, in CCYY-MM-DD format.

+ 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 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility first became available, in CCYY-MM-DD format.

+ References

+ Details

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Data Type:	xbrli:dateItemType
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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

The interest at a per annum rate before including the reserve-adjusted British Banks Association LIBOR Rate.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of limited partner interest units pledged as collateral to guarantee obligations under the credit agreement.

+ References

No definition available.

+ Details

Name:	xtxi_LineOfCreditFacilityCollateralUnits
Namespace Prefix:	xtxi_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage loan to equity value that if not equal or exceeding, borrower may elect to pay interest, fees and expenses in connection with the credit agreement in kind.

+ References

No definition available.

+ Details

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- Definition

Percentage loan to equity value that the borrower must meet by pledging additional collateral if the loan to equity value percentage exceeds 47%.

+ References

No definition available.

+ Details

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- Definition

The fee, expressed as a percentage, equal to terminated commitments multiplied by a fraction the numerator of which is the number of days through March 5, 2016 and the denominator of which is 365.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration