v2.4.1.9

Long-Term Debt Debt Balances and Interest Rates (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013	Jul. 31, 2013	Apr. 29, 2013
Debt Instrument [Line Items]
Net Income free of restrictions under credit agreements	$ 230.3cdw_NetIncomefreeofrestrictionsundercreditagreements
Debt, long-term and short-term	3,192.4us-gaap_DebtInstrumentCarryingAmount
Debt, total long-term and short-term	3,190.0us-gaap_DebtLongtermAndShorttermCombinedAmount		3,251.2us-gaap_DebtLongtermAndShorttermCombinedAmount
Current maturities of long-term debt	(15.4)us-gaap_LongTermDebtCurrent		(45.4)us-gaap_LongTermDebtCurrent
Debt	3,174.6us-gaap_LongTermDebtNoncurrent		3,205.8us-gaap_LongTermDebtNoncurrent
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate	0.00%us-gaap_LongtermDebtWeightedAverageInterestRate / us-gaap_LongtermDebtTypeAxis = us-gaap_RevolvingCreditFacilityMember	[1]
Debt, long-term and short-term	0us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_RevolvingCreditFacilityMember		0us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_RevolvingCreditFacilityMember
Term Loan [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate	3.25%us-gaap_LongtermDebtWeightedAverageInterestRate / us-gaap_LongtermDebtTypeAxis = cdw_TermLoanMember	[1]
Debt, long-term and short-term	1,513.5us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_TermLoanMember		1,528.9us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_TermLoanMember
Debt Instrument, Unamortized Discount	(3.7)us-gaap_DebtInstrumentUnamortizedDiscount / us-gaap_LongtermDebtTypeAxis = cdw_TermLoanMember		(4.4)us-gaap_DebtInstrumentUnamortizedDiscount / us-gaap_LongtermDebtTypeAxis = cdw_TermLoanMember	1.4us-gaap_DebtInstrumentUnamortizedDiscount / us-gaap_LongtermDebtTypeAxis = cdw_TermLoanMember	3.4us-gaap_DebtInstrumentUnamortizedDiscount / us-gaap_LongtermDebtTypeAxis = cdw_TermLoanMember
Senior secured notes due 2018 [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate	0.00%us-gaap_LongtermDebtWeightedAverageInterestRate / us-gaap_LongtermDebtTypeAxis = cdw_SeniorSecuredNotesDue2018Member	[1]
Debt, long-term and short-term	0us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorSecuredNotesDue2018Member		325.0us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorSecuredNotesDue2018Member
Senior notes due 2019 [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate	8.50%us-gaap_LongtermDebtWeightedAverageInterestRate / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesDue2019Member	[1]
Debt, long-term and short-term	503.9us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesDue2019Member		1,305.0us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesDue2019Member
Premium, Unamortized	1.3us-gaap_DebtInstrumentUnamortizedPremium / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesDue2019Member		4.2us-gaap_DebtInstrumentUnamortizedPremium / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesDue2019Member
Senior Notes due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate	6.00%us-gaap_LongtermDebtWeightedAverageInterestRate / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesdue2022Member	[1]
Debt, long-term and short-term	600.0us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesdue2022Member
Premium, Unamortized			0us-gaap_DebtInstrumentUnamortizedPremium / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesdue2022Member
Senior Notes due 2024 [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate	5.50%us-gaap_LongtermDebtWeightedAverageInterestRate / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesdue2024Member	[1]
Debt, long-term and short-term	575.0us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesdue2024Member
Premium, Unamortized			0us-gaap_DebtInstrumentUnamortizedPremium / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesdue2024Member
Subordinated Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate	0.00%us-gaap_LongtermDebtWeightedAverageInterestRate / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember	[1]
Debt, long-term and short-term	$ 0us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember		$ 92.5us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember
[1] Interest rate at December 31, 2014.

X

- Definition

Net Income free of restrictions under credit agreements

+ References

No definition available.

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X

- Definition

Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5



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)

-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 22

-Article 5



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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X

- Definition

The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399



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

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-Name Accounting Standards Codification

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-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

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X

- Definition

The amount of debt premium that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399



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

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X

- Definition

Represents the aggregate of total long-term debt, including current maturities and short-term debt.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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X

- Definition

Amount of long-term debt, after unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. 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 210.5-02.19,20)

-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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19

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X

- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). 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



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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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-Paragraph 22

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X

- Definition

Weighted average interest rate of long-term debt outstanding.

+ References

No definition available.

+ Details

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- Details

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