Long Term Debt (Line of Credit Amendments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012
Leverage Ratios [Abstract]
Senior Leverage Ratio	2.75 to 1.00
Pre May Amendment [Member]
Leverage Ratios [Abstract]
Leverage Ratios	5.0 to 1.0
Post May Amendment [Member]
Leverage Ratios [Abstract]
Leverage Ratios	5.5 to 1.0
Line Of Credit Amendment Date3 [Member]
Leverage Ratios [Abstract]
Allowance For Construction Cost	20.0
Percentage Of Amount of Material Projects	15.00%
Line Of Credit Amendment Date 4 [Member] \| December 31, 2013 and thereafter [Member] \| Minimum Interest Coverage [Member]
Leverage Ratios [Abstract]
Interest Coverge Ratio	2.50 to 1.0
Line Of Credit Amendment Date 4 [Member] \| December 31, 2013 and thereafter [Member] \| Maximum Leverage Ratio [Member]
Leverage Ratios [Abstract]
Leverage Ratios	5.25 to 1.0
Line Of Credit Amendment Date 4 [Member] \| Prior to September 30, 2013 Member [Member] \| Minimum Interest Coverage [Member]
Leverage Ratios [Abstract]
Interest Coverge Ratio	2.25 to 1.0
Line Of Credit Amendment Date 4 [Member] \| Prior to September 30, 2013 Member [Member] \| Maximum Leverage Ratio [Member]
Leverage Ratios [Abstract]
Leverage Ratios	5.50 to 1.0
Letter of Commitment Fee [Member]
Leverage Ratios [Abstract]
Line of Credit Facility, Commitment Fee Percentage	0.50%
Letter of Commitment Fee [Member] \| Greater Than Or Equal To 4.50 To 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	0.50%
Letter of Commitment Fee [Member] \| Greater Than Or Equal To 4.00 To 1.00 And Less Than 4.50 To 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	0.50%
Letter of Commitment Fee [Member] \| Greater Than Or Equal To 3.50 To 1.00 And Less Than 4.00 To 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	0.50%
Letter of Commitment Fee [Member] \| Greater Than Or Equal To 3.00 To 1.00 And Less Than 3.50 To 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	0.50%
Letter of Commitment Fee [Member] \| Less than 3.00 to 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	0.38%
Eurodollar Rate [Member]
Leverage Ratios [Abstract]
Percentage Rate	1.00%
Eurodollar Rate [Member] \| Greater Than Or Equal To 4.50 To 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	3.00%
Eurodollar Rate [Member] \| Greater Than Or Equal To 4.00 To 1.00 And Less Than 4.50 To 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	2.75%
Eurodollar Rate [Member] \| Greater Than Or Equal To 3.50 To 1.00 And Less Than 4.00 To 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	2.50%
Eurodollar Rate [Member] \| Greater Than Or Equal To 3.00 To 1.00 And Less Than 3.50 To 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	2.25%
Eurodollar Rate [Member] \| Less than 3.00 to 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	2.00%
Base Rate [Member]
Leverage Ratios [Abstract]
Percentage Rate	0.50%
Base Rate [Member] \| Greater Than Or Equal To 4.50 To 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	2.00%
Base Rate [Member] \| Greater Than Or Equal To 4.00 To 1.00 And Less Than 4.50 To 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	1.75%
Base Rate [Member] \| Greater Than Or Equal To 3.50 To 1.00 And Less Than 4.00 To 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	1.50%
Base Rate [Member] \| Greater Than Or Equal To 3.00 To 1.00 And Less Than 3.50 To 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	1.25%
Base Rate [Member] \| Less than 3.00 to 1.00 [Member]
Leverage Ratios [Abstract]
Percentage Rate	1.00%
Credit Facility [Member]
Line of Credit Facility [Line Items]
Borrowed under existing credit facility	71.0
Outstanding letter of credit	62.2
Avaliable borrowing capacity	501.8
Leverage Ratios [Abstract]
Line of Credit Facility, Commitment Fee Percentage	0.375%
Available Additional Borrowings	334.6
Credit Facility [Member] \| Preamendment Credit Facility [Member]
Line of Credit Facility [Line Items]
Preamendment borrowing capacity	485.0
Credit Facility [Member] \| Postamendment Credit Facility [Member]
Line of Credit Facility [Line Items]
Postamendment borrowing capacity	635.0
Credit Facility [Member] \| Line Of Credit Amendment Date1 [Member]
Line of Credit Facility [Line Items]
Line of credit facility, amended date	Jan. 01, 2012
Credit Facility [Member] \| Line Of Credit Amendment Date2 [Member]
Line of Credit Facility [Line Items]
Line of credit facility, amended date	May 01, 2012
Credit Facility [Member] \| Line Of Credit Amendment Date3 [Member]
Line of Credit Facility [Line Items]
Line of credit facility, amended date	Aug. 01, 2012
Credit Facility [Member] \| Line Of Credit Amendment Date 4 [Member]
Line of Credit Facility [Line Items]
Line of credit facility, amended date	Jan. 01, 2013

Name:	us-gaap_LeverageRatiosAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount borrowed under the credit facility as of the balance sheet date.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityAmountOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ 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

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Projected EBITDA from material projects allowed in the calculation of Ebitda for purpose or compliance with amended credit agreement minimum

+ References

No definition available.

+ Details

Name:	xtxi_AllowanceForConstructionCost
Namespace Prefix:	xtxi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of additional borrowings currently available based on credit facility covenants.

+ References

No definition available.

+ Details

Name:	xtxi_AvailableAdditionalBorrowings
Namespace Prefix:	xtxi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The ratio of condolidated earnings before interest, taxes, depreciation, amortization, and certain other non-cash charges to consolidated interest charges.

+ References

No definition available.

+ Details

Name:	xtxi_InterestCovergeRatio
Namespace Prefix:	xtxi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of letters of credit issued under the credit facility as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	xtxi_LetterOfCreditFacilityAmountBorrowed
Namespace Prefix:	xtxi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Leverage ratio is defined in the Amended Credit Agreement, being generally computed as the ratio of total funded debt to consolidated earnings before interest, taxes, depreciation, amortization and certain other non-cash charges

+ References

No definition available.

+ Details

Name:	xtxi_LeverageRatios
Namespace Prefix:	xtxi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects when the credit facility was amended, which may be presented in a variety of ways (year, month and year, day, month and year, quarter).

+ References

No definition available.

+ Details

Name:	xtxi_LineOfCreditFacilityAmendedDate
Namespace Prefix:	xtxi_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	xtxi_LineOfCreditInitialBorrowingCapacity
Namespace Prefix:	xtxi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage limitation material project to actual consolidate EBITDA

+ References

No definition available.

+ Details

Name:	xtxi_PercentageOfAmountOfMaterialProjects
Namespace Prefix:	xtxi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Applicable letter of credit fee or interest percentage related to the credit facility.

+ References

No definition available.

+ Details

Name:	xtxi_PercentageRate
Namespace Prefix:	xtxi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined in the Amended Credit Agreement, being generally computed as the ratio of total Secured funded debt to consolidated earnings before interest, taxes, depreciation, amortization and certain other non-cash charges

+ References

No definition available.

+ Details

Name:	xtxi_SeniorLeverageRatio
Namespace Prefix:	xtxi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration