v2.4.1.9

Long-Term Debt Interest Rate Caps (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Cap agreement effective January 14, 2013-2015 [Member]
Derivative [Line Items]
Number of Interest Rate Derivatives Held	10us-gaap_NumberOfInterestRateDerivativesHeld / us-gaap_DerivativeByNatureAxis = cdw_CapAgreementEffectiveJanuary1420132015Member
Derivative Asset, Noncurrent	$ 0us-gaap_DerivativeAssetsNoncurrent / us-gaap_DerivativeByNatureAxis = cdw_CapAgreementEffectiveJanuary1420132015Member
Derivative, Notional Amount	1,150.0invest_DerivativeNotionalAmount / us-gaap_DerivativeByNatureAxis = cdw_CapAgreementEffectiveJanuary1420132015Member
Derivative, Cap Interest Rate	2.40%us-gaap_DerivativeCapInterestRate / us-gaap_DerivativeByNatureAxis = cdw_CapAgreementEffectiveJanuary1420132015Member
Cap agreement effective January 14, 2015-2017 [Member]
Derivative [Line Items]
Number of Interest Rate Derivatives Held	14us-gaap_NumberOfInterestRateDerivativesHeld / us-gaap_DerivativeByNatureAxis = cdw_CapagreementeffectiveJanuary1420152017Member
Derivative Asset, Noncurrent	1.7us-gaap_DerivativeAssetsNoncurrent / us-gaap_DerivativeByNatureAxis = cdw_CapagreementeffectiveJanuary1420152017Member
Derivative, Notional Amount	$ 1,000.0invest_DerivativeNotionalAmount / us-gaap_DerivativeByNatureAxis = cdw_CapagreementeffectiveJanuary1420152017Member

X

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

+ Details

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Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13495-108611



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312



Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Cap rate on an interest rate derivative such as an interest rate cap or collar. If market rates exceed the cap rate, a payment or receipt is triggered on the contract.

+ References

No definition available.

+ Details

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

X

- Details

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

X

- Definition

Number of interest rate derivative instruments held by the entity at the reporting date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5580258-113959



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5579245-113959

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	instant

X

- Details

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Namespace Prefix:
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X

- Details

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