v2.4.1.9

Supplemental Guarantor Information Additional Details (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2014 | May 09, 2014 | Mar. 31, 2014 | Feb. 21, 2014 | Jan. 22, 2014 | Dec. 31, 2013 | Oct. 18, 2013 | Aug. 01, 2013 | Mar. 08, 2013 | Mar. 10, 2010 | Aug. 05, 2014 | Jul. 02, 2013 | Dec. 01, 2014 | Mar. 20, 2014
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Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term Debt, Gross | $ 3,192.4 us-gaap_DebtInstrumentCarryingAmount |  |  |  |  |  |  |  |  |  |  |  |  |
Subordinated Debt [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  | 42.5 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 50.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 20.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 30.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember |  | 155.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 324.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 50.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 28.5 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember |  |  |  |
Long-term Debt, Gross | 0 us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember |  |  |  |  | 92.5 us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember |  |  |  |  |  |  |  |
Senior Notes due 2022 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term Debt, Gross | 600.0 us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesdue2022Member |  |  |  |  |  |  |  |  |  |  |  |  |
Senior secured notes due 2018 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  |  |  |  |  | 325.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorSecuredNotesDue2018Member | 175.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorSecuredNotesDue2018Member |  |
Long-term Debt, Gross | 0 us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorSecuredNotesDue2018Member |  |  |  |  | 325.0 us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorSecuredNotesDue2018Member |  |  |  |  |  |  |  |
Senior notes due 2019 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  |  |  |  |  | 234.7 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesDue2019Member |  | 541.4 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesDue2019Member | 25.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesDue2019Member
Long-term Debt, Gross | 503.9 us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesDue2019Member |  |  |  |  | 1,305.0 us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesDue2019Member |  |  |  |  |  |  |  |
Senior Notes due 2024 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term Debt, Gross | $ 575.0 us-gaap_DebtInstrumentCarryingAmount / us-gaap_LongtermDebtTypeAxis = cdw_SeniorNotesdue2024Member |  |  |  |  |  |  |  |  |  |  |  |  |

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
- Details
Name: | us-gaap_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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
- Details
Name: | us-gaap_LongtermDebtTypeAxis=cdw_SeniorNotesDue2019Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=cdw_SeniorNotesdue2022Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=cdw_SeniorNotesdue2024Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=cdw_SeniorSecuredNotesDue2018Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_SubordinatedDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |