v2.4.1.9

Schedule II Valuation and Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Allowance for Doubtful Accounts [Member] |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | $ 221 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | $ 198 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | $ 202 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember
Additions Charged to Costs and Expenses | 162 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 317 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 293 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember
Deductions from Reserves | 178 us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 294 us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 297 us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember
Balance at End of Year | 205 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 221 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 198 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember
Allowance for Doubtful Accounts [Member] | NBCUniversal Media, LLC [Member] |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | 65 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 46 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 34 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember
Additions Charged to Costs and Expenses | 11 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 33 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 19 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember
Deductions from Reserves | 16 us-gaap_ValuationAllowancesAndReservesDeductions / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 14 us-gaap_ValuationAllowancesAndReservesDeductions / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 7 us-gaap_ValuationAllowancesAndReservesDeductions / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember
Balance at End of Year | 60 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 65 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember | 46 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForDoubtfulAccountsMember
Sales Returns and Allowances [Member] |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | 375 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 307 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 425 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember
Additions Charged to Costs and Expenses | 932 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 811 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 663 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember
Deductions from Reserves | 948 us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 743 us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 781 us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember
Balance at End of Year | 359 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 375 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 307 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember
Sales Returns and Allowances [Member] | NBCUniversal Media, LLC [Member] |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | 372 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 307 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 425 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember
Additions Charged to Costs and Expenses | 930 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 808 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 663 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember
Deductions from Reserves | 946 us-gaap_ValuationAllowancesAndReservesDeductions / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 743 us-gaap_ValuationAllowancesAndReservesDeductions / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 781 us-gaap_ValuationAllowancesAndReservesDeductions / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember
Balance at End of Year | 356 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 372 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember | 307 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_AllowanceForSalesReturnsMember
Deferred Tax Valuation Allowance |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | 405 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 355 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 297 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember
Additions Charged to Costs and Expenses | 33 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 71 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 61 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember
Deductions from Reserves | 63 us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 21 us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 3 us-gaap_ValuationAllowancesAndReservesDeductions / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember
Balance at End of Year | 375 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 405 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 355 us-gaap_ValuationAllowancesAndReservesBalance / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember
Deferred Tax Valuation Allowance | NBCUniversal Media, LLC [Member] |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | 60 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 73 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 53 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember
Additions Charged to Costs and Expenses | 33 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 8 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 23 us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember
Deductions from Reserves | 6 us-gaap_ValuationAllowancesAndReservesDeductions / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 21 us-gaap_ValuationAllowancesAndReservesDeductions / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | 3 us-gaap_ValuationAllowancesAndReservesDeductions / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember
Balance at End of Year | $ 87 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | $ 60 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember | $ 73 us-gaap_ValuationAllowancesAndReservesBalance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember

X
- Definition Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 09 -Article 12 + Details
Name: | us-gaap_ValuationAllowancesAndReservesBalance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, charged to costs and expenses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 09 -Article 12 + Details
Name: | us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 09 -Article 12 + Details
Name: | us-gaap_ValuationAllowancesAndReservesDeductions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

X
- Details
Name: | us-gaap_ValuationAllowancesAndReservesTypeAxis=us-gaap_AllowanceForDoubtfulAccountsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ValuationAllowancesAndReservesTypeAxis=us-gaap_AllowanceForSalesReturnsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ValuationAllowancesAndReservesTypeAxis=us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |