v2.4.1.9

Investments (Details) (USD $) In Millions, unless otherwise specified | Mar. 31, 2015 | Dec. 31, 2014
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Fair value method | $ 182 us-gaap_MarketableSecurities | $ 662 us-gaap_MarketableSecurities
Equity method | 1,149 us-gaap_EquityMethodInvestments | 1,019 us-gaap_EquityMethodInvestments
Cost method | 2,062 us-gaap_CostMethodInvestments | 2,056 us-gaap_CostMethodInvestments
Total Investments | 3,393 us-gaap_Investments | 3,737 us-gaap_Investments
Less: Current investments | 158 us-gaap_ShortTermInvestments | 602 us-gaap_ShortTermInvestments
Noncurrent investments | 3,235 us-gaap_LongTermInvestments | 3,135 us-gaap_LongTermInvestments
NBCUniversal Media, LLC [Member] |  |
Fair value method | 10 us-gaap_MarketableSecurities / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember | 10 us-gaap_MarketableSecurities / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Equity method | 971 us-gaap_EquityMethodInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember | 840 us-gaap_EquityMethodInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Cost method | 24 us-gaap_CostMethodInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember | 32 us-gaap_CostMethodInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Total Investments | 1,005 us-gaap_Investments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember | 882 us-gaap_Investments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Less: Current investments | 52 us-gaap_ShortTermInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember | 0 us-gaap_ShortTermInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Noncurrent investments | 953 us-gaap_LongTermInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember | 882 us-gaap_LongTermInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Air Touch [Member] |  |
Cost method | 1,572 us-gaap_CostMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_AirTouchMember | 1,568 us-gaap_CostMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_AirTouchMember
Other Investment [Member] |  |
Equity method | 534 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_OtherInvestmentMember | 517 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_OtherInvestmentMember
Cost method | 490 us-gaap_CostMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_OtherInvestmentMember | 488 us-gaap_CostMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_OtherInvestmentMember
Other Investment [Member] | NBCUniversal Media, LLC [Member] |  |
Equity method | 356 us-gaap_EquityMethodInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_OtherInvestmentMember | 338 us-gaap_EquityMethodInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_OtherInvestmentMember
The Weather Channel [Member] |  |
Equity method | 336 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_WeatherChannelMember | 335 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_WeatherChannelMember
The Weather Channel [Member] | NBCUniversal Media, LLC [Member] |  |
Equity method | 336 us-gaap_EquityMethodInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_WeatherChannelMember | 335 us-gaap_EquityMethodInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_WeatherChannelMember
Hulu [Member] |  |
Equity method | 279 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_HuluMember | 167 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_HuluMember
Hulu [Member] | NBCUniversal Media, LLC [Member] |  |
Equity method | $ 279 us-gaap_EquityMethodInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_HuluMember | $ 167 us-gaap_EquityMethodInvestments / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cmcsa_HuluMember

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- Definition Amount, after adjustment, of cost-method investment. Adjustments include, but are not limited to, dividends received in excess of earnings after date of investment that are considered a return of investment and other than temporary impairments. + 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 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 325 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6872867&loc=d3e40691-111596 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 325 -SubTopic 20 -Section 35 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=29638308&loc=d3e40346-111594 + Details
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- Definition This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized. + 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 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35755396&loc=d3e33749-111570 + Details
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- Definition The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle). + 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 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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