Amount owed under Revolving loan financing agreement

No definition available.

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Balance Type:	credit
Period Type:	instant

- Definition

Cash Availability, Percentage of Borrowing Base

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Fixed Charge Coverage Ratio

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Floorplan sub-facility

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Floorplan sub-facility, reserve

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Floorplan sub-facility, variation between balance in financials and balance per financial intermediary due to timing differences in reporting

+ References

No definition available.

+ Details

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

- Definition

Line of Credit Facility, Borrowing Base

+ References

No definition available.

+ Details

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Namespace Prefix:	cdw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of Credit Facility, Decrease in Applicable Interest Rate Margin, Basis Points

+ References

No definition available.

+ Details

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Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Line of Credit Facility, Fee on Unused Portion, Basis Points

+ References

No definition available.

+ Details

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Namespace Prefix:	cdw_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Line Of Credit Facility, Maximum Aggregate Increase

+ References

No definition available.

+ Details

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Namespace Prefix:	cdw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Minimum Liquidity Condition, Amount

+ References

No definition available.

+ Details

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

- Definition

Minimum Liquidity Condition, Cash Availability

+ References

No definition available.

+ Details

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Namespace Prefix:	cdw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage reserve for open orders under financing agreement

+ References

No definition available.

+ Details

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Namespace Prefix:	cdw_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Potential Margin Reduction

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Revolving Loan, Consecutive Business Days Below Minimum Average Daily Excess Cash Availability Requirement

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
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Period Type:	duration

- Definition

Revolving Loan financing agreement

+ References

No definition available.

+ Details

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Namespace Prefix:	cdw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Revolving Loan Maturity Acceleration Provision, Days Prior to Maturity

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Revolving Loan Maturity Acceleration Provision, Excess Cash Availability Limit, Amount Plus Maturing Debt

+ References

No definition available.

+ Details

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

- Definition

Revolving Loan, Minimum Average Daily Excess Cash Availability Requirement, Consecutive Business Days Met

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Variable Interest Rate, ABR Determination, Basis Point Plus Federal Funds Effective Rate

+ References

No definition available.

+ Details

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Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Variable Interest Rate, ABR Determination, Percentage Plus One-Month LIBOR

+ References

No definition available.

+ Details

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Namespace Prefix:	cdw_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Variable Interest Rate Margin

+ References

No definition available.

+ Details

Name:	cdw_VariableInterestRateMargin
Namespace Prefix:	cdw_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

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-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

-Section 03

-Paragraph 16

-Article 9

+ Details

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

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For an unclassified balance sheet, the carrying amount (net of accumulated amortization) as of the balance sheet date of capitalized costs associated with the issuance of debt instruments (for example, legal, accounting, underwriting, printing, and registration costs) that will be charged against earnings over the life of the debt instruments to which such costs pertain.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28555-108399

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.17)

-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 17

-Article 5

+ Details

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

- Definition

Net amount of long-term deferred finance costs capitalized at the end of the reporting period.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 50

-Section 40

-Paragraph 2

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 50

-Section 40

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6850294&loc=d3e12355-112629

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

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

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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

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

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Long-Term Debt Revolving Loan (Details) (USD $)	12 Months Ended			3 Months Ended
Long-Term Debt Revolving Loan (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Sep. 30, 2014	Jul. 31, 2013
Debt Instrument [Line Items]
Debt, long-term and short-term	$ 3,192,400,000us-gaap_DebtInstrumentCarryingAmount			$ 3,192,400,000us-gaap_DebtInstrumentCarryingAmount
Gains (Losses) on Extinguishment of Debt	90,700,000	64,000,000	17,200,000
Deferred Finance Costs, Noncurrent, Net	33,000,000	30,100,000	53,200,000	33,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt, long-term and short-term	0	0		0
Letters of Credit Outstanding, Amount	2,100,000			2,100,000
Floorplan sub-facility, reserve	312,300,000			312,300,000
Line of Credit Facility, Maximum Borrowing Capacity	1,250,000,000.0			1,250,000,000.0
Line of Credit Facility, Fee on Unused Portion, Basis Points	25			25
Line of Credit Facility, Decrease in Applicable Interest Rate Margin, Basis Points					50
Gains (Losses) on Extinguishment of Debt	400,000
Deferred Finance Costs, Noncurrent, Net	6,400,000			6,400,000
Variable Interest Rate Margin, ABR Determination, Basis Point Plus Federal Funds Effective Rate	50			50
Variable Interest Rate Margin, ABR Determination, Percentage Plus LIBOR	1.00%			1.00%
Potential Margin Reduction	0.25%			0.25%
Line of Credit Facility, Borrowing Base	1,253,400,000			1,253,400,000
Line of Credit Facility, Remaining Borrowing Capacity	935,600,000			935,600,000
Revolving Loan, Consecutive Business Days Below Minimum Average Daily Excess Cash Availability Requirement	5 days
Revolving Loan, Minimum Average Daily Excess Cash Availability Requirement, Consecutive Business Days Met	30 days
Line Of Credit Facility, Maximum Aggregate Increase	300,000,000			300,000,000
Revolving Loan Maturity Acceleration Provision, Days Prior to Maturity				45 days
Revolving Loan Maturity Acceleration Provision, Excess Cash Availability Limit, Amount Plus Maturing Debt	150,000,000			150,000,000
Minimum Liquidity Condition, Cash Availability	125,000,000			125,000,000
Cash Availability, Percentage of Borrowing Base	10.00%			10.00%
Minimum Liquidity Condition, Amount	100,000,000			100,000,000
Fixed Charge Coverage Ratio	1.00			1.00
Previous Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	900,000,000			900,000,000
Line Of Credit Facility, Maximum Aggregate Increase	200,000,000			200,000,000
Term Loan [Member]
Debt Instrument [Line Items]
Debt, long-term and short-term	1,513,500,000	1,528,900,000		1,513,500,000
Gains (Losses) on Extinguishment of Debt		10,300,000
Deferred Finance Costs, Net						6,100,000
Higher Utilization [Member] \| Previous Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Fee on Unused Portion, Basis Points	37.5			37.5
Lower Utilization [Member] \| Previous Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Fee on Unused Portion, Basis Points	50			50
LIBOR [Member] \| Minimum [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Variable Interest Rate Margin	1.50%			1.50%
LIBOR [Member] \| Minimum [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Variable Interest Rate Margin	2.25%			2.25%
LIBOR [Member] \| Maximum [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Variable Interest Rate Margin	2.00%			2.00%
LIBOR [Member] \| Maximum [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Variable Interest Rate Margin	2.50%			2.50%
ABR [Member] \| Minimum [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Variable Interest Rate Margin	0.50%			0.50%
ABR [Member] \| Minimum [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Variable Interest Rate Margin	1.25%			1.25%
ABR [Member] \| Maximum [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Variable Interest Rate Margin	1.00%			1.00%
ABR [Member] \| Maximum [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Variable Interest Rate Margin	1.50%			1.50%
Accounts Payable, Inventory Financing [Member]
Debt Instrument [Line Items]
Revolving Loan financing agreement	330,100,000	256,100,000		330,100,000
Accounts Payable, Inventory Financing [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Amount owed under Revolving loan financing agreement	312,300,000			312,300,000
Floorplan sub-facility, variation in balance due to timing	17,800,000			17,800,000
Accounts Payable, Inventory Financing [Member] \| Previous Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Floorplan sub-facility	$ 400,000,000			$ 400,000,000
Percentage reserve for open orders under financing agreement					15.00%