v2.4.0.8

Subsequent Events (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended			3 Months Ended	9 Months Ended				0 Months Ended		1 Months Ended	3 Months Ended											1 Months Ended		9 Months Ended				3 Months Ended	9 Months Ended						0 Months Ended	3 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Aug. 05, 2014 Senior Notes [Member]	Sep. 30, 2014 Senior Secured Notes, due 2018 [Member]	Sep. 30, 2013 Senior Secured Notes, due 2018 [Member]	Aug. 05, 2014 Senior Secured Notes, due 2018 [Member]	Dec. 31, 2013 Senior Secured Notes, due 2018 [Member]	Jul. 02, 2013 Senior Secured Notes, due 2018 [Member]	May 09, 2014 Subordinated Debt [Member]	Mar. 08, 2013 Subordinated Debt [Member]	Feb. 28, 2014 Subordinated Debt [Member]	Sep. 30, 2014 Subordinated Debt [Member]	Mar. 31, 2014 Subordinated Debt [Member]	Dec. 31, 2013 Subordinated Debt [Member]	Sep. 30, 2013 Subordinated Debt [Member]	May 09, 2014 Subordinated Debt [Member]	Feb. 21, 2014 Subordinated Debt [Member]	Jan. 22, 2014 Subordinated Debt [Member]	Oct. 18, 2013 Subordinated Debt [Member]	Aug. 01, 2013 Subordinated Debt [Member]	Mar. 08, 2013 Subordinated Debt [Member]	Mar. 10, 2010 Subordinated Debt [Member]	Jul. 31, 2013 Term Loan [Member]	Apr. 30, 2013 Term Loan [Member]	Sep. 30, 2013 Term Loan [Member]	Sep. 30, 2014 Term Loan [Member]	Dec. 31, 2013 Term Loan [Member]	Apr. 29, 2013 Term Loan [Member]	Sep. 30, 2014 Senior notes due 2019 [Member]	Sep. 30, 2014 Senior notes due 2019 [Member]	Aug. 05, 2014 Senior notes due 2019 [Member]	Mar. 20, 2014 Senior notes due 2019 [Member]	Dec. 31, 2013 Senior notes due 2019 [Member]	Sep. 30, 2014 LIBOR [Member] Minimum [Member] Term Loan [Member]	Sep. 30, 2014 LIBOR [Member] Maximum [Member] Term Loan [Member]	Nov. 12, 2014 Subsequent Event [Member]	Dec. 31, 2014 Subsequent Event [Member]	Nov. 06, 2014 Subsequent Event [Member]	Dec. 31, 2014 Cap agreement effective January 14, 2015-2017 [Member] Subsequent Event [Member]	Sep. 30, 2014 Interest rate cap purchased during 2014 [Member]	Dec. 31, 2014 Interest rate cap purchased during 2014 [Member] Subsequent Event [Member]
Subsequent Event [Line Items]
Derivative, Notional Amount																																									$ 300,000,000	$ 250,000,000
Derivative Asset entered into during fourth quarter 2014, noncurrent			700,000	0																																			600,000
Interest Rate Cap, cap rate																																										2.00%	2.00%
Cash dividends declared per common share																																							$ 0.0675
Proceeds from Issuance of Debt																									190,000,000
Debt Instrument, Repurchased Face Amount								325,000,000		175,000,000					50,000,000			42,500,000	20,000,000	30,000,000	155,000,000	324,000,000	50,000,000	28,500,000									234,700,000	25,000,000
Redemption Premium, percentage of par value								0.00%		108.00%								104.178%	104.178%		104.178%	106.268%	106.268%										108.80%	109.75%
Extinguishment of Debt, Accrued Interest Paid to Lenders										700,000								400,000	1,900,000		200,000	12,000,000	2,500,000											1,000,000
Proceeds from Issuance of Long-term Debt			600,000,000	1,535,200,000																						1,350,000,000
Debt, short-term and long-term					600,000,000	0			325,000,000					0		92,500,000												1,517,400,000	1,528,900,000		1,045,300,000	1,045,300,000			1,305,000,000
Long-term Debt, stated interest rate						8.00%								12.535%																	8.50%	8.50%
Discount, percent of par																									99.25%					99.75%
Variable Interest Rate Margin																																				2.25%	2.50%
Quarterly amortization payment of original principal, Percent																												0.25%
Net loss on extinguishments of long-term debt	45,800,000	41,300,000	53,800,000	55,500,000		(23,700,000)	16,700,000					3,900,000		(2,200,000)	2,700,000	8,500,000	24,600,000										10,300,000				(22,100,000)	(2,700,000)
Extinguishment of Debt, Fees Paid to Lenders						13,000,000	14,000,000				1,800,000	3,100,000			2,100,000	6,500,000	20,300,000														10,000,000	2,400,000
Write off of Deferred Debt Issuance Cost						4,000,000	2,700,000					800,000	600,000	400,000		2,000,000	4,300,000														2,200,000	300,000
Debt Instrument, Repurchase Amount																																	234,700,000
Stock Repurchase Program, Number of Shares Authorized to be Repurchased																																								$ 500,000,000
Stock Repurchased During Period, Shares																																						0
Equity Method Investment, Ownership Percentage																																								35.00%

X

- Definition

Discount, percent of par

+ References

No definition available.

+ Details

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

X

- Definition

Extinguishment of Debt, Accrued Interest Paid to Lenders

+ References

No definition available.

+ Details

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

X

- Definition

Extinguishment of Debt, Fees Paid to Lenders

+ References

No definition available.

+ Details

Name:	cdw_ExtinguishmentOfDebtFeesPaidToLenders
Namespace Prefix:	cdw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Quarterly amortization payment of original principal, Percent

+ References

No definition available.

+ Details

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

X

- Definition

Redemption Premium, percentage of par value

+ References

No definition available.

+ Details

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

X

- 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

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

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

X

- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

+ Details

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

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

-Section 03

-Paragraph 16

-Article 9

+ Details

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

X

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-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(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

X

- Definition

Fair value amount of debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchaseAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchasedFaceAmount
Namespace Prefix:	us-gaap_
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

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

X

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

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

X

- 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



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 50

-Section 40

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6850294&loc=d3e12317-112629



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

-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

Name:	us-gaap_GainsLossesOnExtinguishmentOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

The cash outflow for derivative instruments during the period, which are classified as investing activities, excluding those designated as hedging instruments.

+ References

No definition available.

+ Details

Name:	us-gaap_PaymentsForDerivativeInstrumentInvestingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

No definition available.

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Number of shares that have been repurchased and retired during the period.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644



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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

+ Details

Name:	us-gaap_StockRepurchasedAndRetiredDuringPeriodShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of stock repurchase plan authorized.

+ References

No definition available.

+ Details

Name:	us-gaap_StockRepurchaseProgramAuthorizedAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Details

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

X

- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

Name:	us-gaap_WriteOffOfDeferredDebtIssuanceCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration