Represents the maximum ratio of consolidated total debt to adjusted EBITDA.

No definition available.

Name:	exh_DebtInstrumentFinancialCovenantMaximumConsolidatedTotalDebtToAdjustedEBITDARatio
Namespace Prefix:	exh_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the maximum ratio of senior secured debt to adjusted EBITDA.

+ References

No definition available.

+ Details

Name:	exh_DebtInstrumentFinancialCovenantMaximumSeniorSecuredDebtToAdjustedEBITDA
Namespace Prefix:	exh_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the minimum ratio of adjusted EBITDA to total interest expense.

+ References

No definition available.

+ Details

Name:	exh_DebtInstrumentFinancialCovenantMinimumAdjustedEBITDAToTotalInterestExpensesRatio
Namespace Prefix:	exh_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum amount of additional aggregate commitments allowed under the credit facility which is subject to certain conditions and with the approval of the lenders.

+ References

No definition available.

+ Details

Name:	exh_LineOfCreditFacilityAdditionalCommitmentsMaximum
Namespace Prefix:	exh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets) and considering any amounts currently outstanding.

+ References

No definition available.

+ Details

Name:	exh_LineOfCreditFacilityCurrentAvailableBorrowingCapacity
Namespace Prefix:	exh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the percentage of equity interests in first tier foreign subsidiaries held by the entity used to secure borrowings.

+ References

No definition available.

+ Details

Name:	exh_PercentageOfEquityInterestsInFirstTierForeignSubsidiaries
Namespace Prefix:	exh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

- Definition

Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
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 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_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

+ Details

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

- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

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 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

Name:	us-gaap_WriteOffOfDeferredDebtIssuanceCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Long-Term Debt (Details 2) (Revolving credit facility due July 2016, USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended	12 Months Ended
	Jul. 31, 2011	Mar. 31, 2012	Dec. 31, 2014	Dec. 31, 2013
Long-Term Debt
Expiration period of credit facility	5 years
Revolving credit facility borrowing capacity	$ 1,100.0	$ 900.0
Write-off of deferred financing costs		1.3
Weighted average annual interest rate (as a percent)			1.70%us-gaap_DebtWeightedAverageInterestRate	1.70%us-gaap_DebtWeightedAverageInterestRate
Outstanding borrowings			375.5us-gaap_LineOfCredit
Outstanding letters of credit			93.9
Undrawn capacity under revolving credit facility			430.6
Available borrowings under revolving credit facility			430.6
Percentage of equity interests in first tier foreign subsidiaries			65.00%
Maximum additional commitment amount			$ 300.0
Minimum adjusted EBITDA to total interest expense ratio			2.25
Maximum consolidated total debt to adjusted EBITDA ratio			5.0
Maximum senior secured debt to EBITDA ratio			4.0
LIBOR
Long-Term Debt
Debt instrument, basis spread on variable rate (as a percent)			1.50%
LIBOR \| Minimum
Long-Term Debt
Debt instrument, basis spread on variable rate (as a percent)			1.50%
LIBOR \| Maximum
Long-Term Debt
Debt instrument, basis spread on variable rate (as a percent)			2.50%
Base rate loans \| Minimum
Long-Term Debt
Debt instrument, basis spread on variable rate (as a percent)			0.50%
Base rate loans \| Maximum
Long-Term Debt
Debt instrument, basis spread on variable rate (as a percent)			1.50%
Federal Funds
Long-Term Debt
Debt instrument, basis spread on variable rate (as a percent)			0.50%
one-month LIBOR
Long-Term Debt
Debt instrument, basis spread on variable rate (as a percent)			1.00%