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Income Taxes (Details 8) (USD $) In Millions, unless otherwise specified | 12 Months Ended | 1 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2014 | Dec. 31, 2012 | Oct. 31, 2012
Unrecognized tax benefits , which if recognized would affect the effective tax rate | $ 14.6 us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate | 11.3 us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate |  | $ 9.6 us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate |
Potential interest expense and penalties related to unrecognized tax benefits | 3.3 us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued | 3.4 us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued |  | 2.4 us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued |
Aggregate over assessment on income tax examination |  |  |  |  | 0.9 us-gaap_IncomeTaxExaminationIncreaseDecreaseInLiabilityFromPriorYear
Amount of disallowance of telephone excise tax refund claims for which protests were filed with the Appeals Division of the IRS |  |  |  |  | 0.5 exh_IncomeTaxExaminationAmountForWhichProtestsWereFiledWithAppealsDivision
Refund of over-assessment received |  |  | 0.9 us-gaap_IncomeTaxExaminationLiabilityRefundAdjustmentFromSettlementWithTaxingAuthority |  |
State income tax returns, period subject to examination, low end of range | 3 years |  |  |  |
State income tax returns, period subject to examination, high end of range | 5 years |  |  |  |
State income tax examination period after formal notification, maximum | 1 year |  |  |  |
Maximum reasonably possible decrease in unrecognized tax benefits | $ 0.1 us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleEstimatedRangeOfChangeUpperBound |  |  |  |
IRS | Minimum |  |  |  |  |
Percentage of telephone excise tax refund claims settled |  | 90.00%exh_PercentageOfTelephoneExciseTaxRefundClaimsSettled / us-gaap_IncomeTaxAuthorityNameAxis = us-gaap_InternalRevenueServiceIRSMember / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |

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- Definition Represents the increase or decrease in prior year liability for amounts for which protest was filed with appeals division of the IRS. + References No definition available. + Details
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- Definition Represents maximum period of income tax examination after formal notification. + References No definition available. + Details
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- Definition Represents the high end of the range period for which state income tax returns are subject to examination after filing. + References No definition available. + Details
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- Definition Represents the low end of the range period for which state income tax returns are subject to examination after filing. + References No definition available. + Details
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- Definition Represents the percentage of telephone excise tax refund claims settled. + References No definition available. + Details
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- Definition The amount the liability recorded for the income tax examination increased or decreased in the current year/accounting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319 + Details
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- Definition The amount of the additional liability or refund received or expected based on a final settlement with a taxing authority. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319 + Details
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- Definition Amount of (increase) decrease reasonably possible in the estimated upper bound of the unrecognized tax benefit for a tax position taken or expected to be taken. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319 + Details
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- Definition Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319 + Details
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- Definition The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
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