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Long-Term Debt (Details) (USD $) | 12 Months Ended | 0 Months Ended |
--- | --- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Feb. 28, 2014 | May 16, 2013
Debt Instrument [Line Items] |  |  |  |  |
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months | $ 18,250,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths |  |  |  |
Document Period End Date | Dec. 31, 2014 |  |  |  |
Senior Secured Debt | 415,125,000 us-gaap_SecuredDebt | 399,813,000 us-gaap_SecuredDebt |  |  |
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums |  | 15,000,000 us-gaap_UnamortizedLoanCommitmentAndOriginationFeesAndUnamortizedDiscountsOrPremiums |  |  |
Write off of Deferred Debt Issuance Cost | 0 us-gaap_WriteOffOfDeferredDebtIssuanceCost | 14,958,000 us-gaap_WriteOffOfDeferredDebtIssuanceCost | 813,000 us-gaap_WriteOffOfDeferredDebtIssuanceCost |  |
Pledged equity interest in foreign subsidiaries | 65.00%asgn_Pledgedequityinterestinforeignsubsidiaries |  |  |  |
Weighted average interest rate | 2.60%us-gaap_DebtWeightedAverageInterestRate |  |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Two | 18,250,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo |  |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Three | 18,250,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree |  |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Four | 180,063,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour |  |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Five | 0 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive |  |  |  |
Long-term Debt, Maturities, Repayments of Principal after Year Five | 180,312,000 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive |  |  |  |
Long-term Debt | 415,125,000 us-gaap_LongTermDebt |  |  |  |
Maximum [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Leverage Ratio in Latest Year of Debt Term | 3.25 asgn_LeverageRatioinLatestYearofDebtTerm / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  |
Leverage ratio | 3.50 asgn_LeverageRatio / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  |
Revolving Loans and Term A Loans | Eurodollar Rate or Base Rate [Member] | Maximum [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Basis spread on variable rate borrowings | 2.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = asgn_RevolvingLoansAndTermLoansMember / asgn_InterestRateTypeAxis = asgn_EurodollarRateorBaseRateMember / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  |
Revolving Loans and Term A Loans | Eurodollar Rate or Base Rate [Member] | Minimum [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Basis spread on variable rate borrowings | 1.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = asgn_RevolvingLoansAndTermLoansMember / asgn_InterestRateTypeAxis = asgn_EurodollarRateorBaseRateMember / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |  |
Term A Loans, Term B Loans and Revolving Loans [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Line of credit facility, maximum borrowing capacity |  |  |  |  | 500,000,000 us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity / us-gaap_DebtInstrumentAxis = asgn_TermALoansTermBLoansandRevolvingLoansMember
Term-B Loan Facility due May 2020 [Member] | Eurodollar [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Basis spread on variable rate borrowings | 2.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = asgn_TermBLoanFacilitydueMay2020Member / asgn_InterestRateTypeAxis = us-gaap_EurodollarMember |  |  |  |
Term Loan Facility | $100 million term A loan facility, due May 2017 |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Interest rate at year end | 1.90%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = asgn_TermALoanFacilityDueMay2017Member / us-gaap_LongtermDebtTypeAxis = us-gaap_NotesPayableToBanksMember |  |  |  |
Term Loan Facility | Term A Loans, Term B Loans and Revolving Loans [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Increase to borrowing capacity available under credit facility |  |  |  |  | 100,000,000 asgn_LineOfCreditFacilityIncreaseInAdditionalPrincipalAmount / us-gaap_DebtInstrumentAxis = asgn_TermALoansTermBLoansandRevolvingLoansMember / us-gaap_LongtermDebtTypeAxis = us-gaap_NotesPayableToBanksMember
Term Loan Facility | Term-A Loan Facility due May 2018 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Senior Secured Debt | 158,813,000 us-gaap_SecuredDebt / us-gaap_DebtInstrumentAxis = asgn_TermALoanFacilitydueMay2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_NotesPayableToBanksMember | 92,500,000 us-gaap_SecuredDebt / us-gaap_DebtInstrumentAxis = asgn_TermALoanFacilitydueMay2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_NotesPayableToBanksMember |  |  |
Face amount of term loan |  |  |  |  | 100,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = asgn_TermALoanFacilitydueMay2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_NotesPayableToBanksMember
Secured Debt, Increase in Additional Principal Amount |  |  |  | 82,500,000 asgn_SecuredDebtIncreaseinAdditionalPrincipalAmount / us-gaap_DebtInstrumentAxis = asgn_TermALoanFacilitydueMay2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_NotesPayableToBanksMember |
Term Loan Facility | Term-B Loan Facility due May 2020 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Senior Secured Debt | 180,312,000 us-gaap_SecuredDebt / us-gaap_DebtInstrumentAxis = asgn_TermBLoanFacilitydueMay2020Member / us-gaap_LongtermDebtTypeAxis = us-gaap_NotesPayableToBanksMember | 262,813,000 us-gaap_SecuredDebt / us-gaap_DebtInstrumentAxis = asgn_TermBLoanFacilitydueMay2020Member / us-gaap_LongtermDebtTypeAxis = us-gaap_NotesPayableToBanksMember |  |  |
Face amount of term loan |  |  |  |  | 275,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = asgn_TermBLoanFacilitydueMay2020Member / us-gaap_LongtermDebtTypeAxis = us-gaap_NotesPayableToBanksMember
Repayments of Lines of Credit |  |  |  | 82,500,000 us-gaap_RepaymentsOfSecuredDebt / us-gaap_DebtInstrumentAxis = asgn_TermBLoanFacilitydueMay2020Member / us-gaap_LongtermDebtTypeAxis = us-gaap_NotesPayableToBanksMember |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  | 1.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = asgn_TermBLoanFacilitydueMay2020Member / us-gaap_LongtermDebtTypeAxis = us-gaap_NotesPayableToBanksMember
Interest rate at year end | 3.50%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = asgn_TermBLoanFacilitydueMay2020Member / us-gaap_LongtermDebtTypeAxis = us-gaap_NotesPayableToBanksMember |  |  |  |
Revolving Credit Facility |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Letters of credit outstanding, amount | 45,800,000 us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity / us-gaap_LongtermDebtTypeAxis = us-gaap_RevolvingCreditFacilityMember |  |  |  |
Revolving Credit Facility | Revolving Credit Facility due May 2018 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Senior Secured Debt | 76,000,000 us-gaap_SecuredDebt / us-gaap_DebtInstrumentAxis = asgn_RevolvingCreditFacilitydueMay2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_RevolvingCreditFacilityMember | 44,500,000 us-gaap_SecuredDebt / us-gaap_DebtInstrumentAxis = asgn_RevolvingCreditFacilitydueMay2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_RevolvingCreditFacilityMember |  |  |
Line of credit facility, maximum borrowing capacity |  |  |  |  | $ 125,000,000 us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity / us-gaap_DebtInstrumentAxis = asgn_RevolvingCreditFacilitydueMay2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_RevolvingCreditFacilityMember
Revolving Credit Facility | Revolving Credit Facility due May 2018 [Member] | Maximum [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Revolving credit facility, unused portion, commitment fee percentage | 0.40%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage / us-gaap_DebtInstrumentAxis = asgn_RevolvingCreditFacilitydueMay2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_RevolvingCreditFacilityMember / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  |
Revolving Credit Facility | Revolving Credit Facility due May 2018 [Member] | Minimum [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Revolving credit facility, unused portion, commitment fee percentage | 0.25%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage / us-gaap_DebtInstrumentAxis = asgn_RevolvingCreditFacilitydueMay2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_RevolvingCreditFacilityMember / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |  |
Revolving Credit Facility | Revolving Credit Facility due May 2018 [Member] | Base Rate [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Interest rate at year end | 0.17%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = asgn_RevolvingCreditFacilitydueMay2018Member / asgn_InterestRateTypeAxis = us-gaap_BaseRateMember / us-gaap_LongtermDebtTypeAxis = us-gaap_RevolvingCreditFacilityMember |  |  |  |
Revolving Credit Facility | Revolving Credit Facility due May 2018 [Member] | Spread [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Interest rate at year end | 2.00%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = asgn_RevolvingCreditFacilitydueMay2018Member / asgn_InterestRateTypeAxis = asgn_SpreadMember / us-gaap_LongtermDebtTypeAxis = us-gaap_RevolvingCreditFacilityMember |  |  |  |

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- Definition The leverage ratio as defined in the credit agreement. + References No definition available. + Details
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- Definition Leverage ratio limit in latest year of debt facility, as described in debt agreement. + References No definition available. + Details
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- Definition Line of Credit Facility, Increase in Additional Principal Amount + References No definition available. + Details
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- Definition The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented. If there is no historical data in the report, use the filing date. The format of the date is CCYY-MM-DD. + References No definition available. + Details
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- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
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- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400 + Details
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- Definition Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399 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 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + 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 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Weighted average interest rate of debt outstanding. + References No definition available. + Details
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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 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 + Details
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- 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 + Details
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- 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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- Definition Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + 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 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: 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 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 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition The cash outflow to repay long-term debt that is wholly or partially secured by collateral. Excludes repayments of tax exempt secured debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 + Details
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