v3.7.0.1

Investments | 3 Months Ended
--- | ---
Mar. 31, 2017
Fair Value, Equity And Cost Method Investments [Line Items] |
Investments | Investments
(in millions) | March 31, 2017 | December 31, 2016
Fair Value Method: |  |
Snap | $ | 662 |  | $ | — |
Other | 161 |  | 198 |
| 823 |  | 198 |
Equity Method: |  |  |  |
Atairos | 1,624 |  | 1,601 |
Hulu | 171 |  | 225 |
Other | 631 |  | 550 |
| 2,426 |  | 2,376 |
Cost Method: |  |
AirTouch | 1,602 |  | 1,599 |
BuzzFeed | 400 |  | 400 |
Other | 698 |  | 771 |
| 2,700 |  | 2,770 |
Total investments | 5,949 |  | 5,344 |
Less: Current investments | 11 |  | 97 |
Noncurrent investments | $ | 5,938 |  | $ | 5,247 |
Investment Income (Loss), Net
| Three Months Ended March 31
(in millions) | 2017 | 2016
Gains (losses) on sales and exchanges of investments, net | $ | (1 | ) | $ | 2 |
Investment impairment losses | (4 | ) | (20 | )
Interest and dividend income | 33 |  | 29 |
Other, net | 31 |  | 19 |
Investment income (loss), net | $ | 59 |  | $ | 30 |
Fair Value Method Snap In March 2017, we acquired an interest in Snap Inc. for $500 million as part of its initial public offering, which we have classified as available for sale. Snap is a camera company whose primary product is Snapchat, a camera app that was created to help people communicate through short videos and images. Equity Method Atairos For the three months ended March 31, 2017, we made cash capital contributions totaling $457 million to Atairos Group, Inc., which included amounts accrued as of December 31, 2016. Atairos follows investment company accounting and records its investments at their fair values each reporting period with the net gains or losses reflected in its statement of income. We recognize our share of these gains and losses in equity in net income (losses) of investees, net. For the three months ended March 31, 2017, we recognized our share of Atairos income of $57 million. For the three months ended March 31, 2016, we recognized our share of Atairos losses of $15 million. The Weather Channel In January 2016, following a legal restructuring at The Weather Channel, we and the other investors sold the entity holding The Weather Channel’s product and technology businesses to IBM. Following the close of the transaction, we continue to hold an investment in The Weather Channel cable network through a new holding company. As a result of the sale of our investment, we recognized a pretax gain of $108 million in other income (expense), net for the three months ended March 31, 2016. Cost Method AirTouch We hold two series of preferred stock of Verizon Americas, Inc., formerly known as AirTouch Communications, Inc. (“AirTouch”), a subsidiary of Verizon Communications Inc., which are redeemable in April 2020. As of March 31, 2017, the estimated fair value of the AirTouch preferred stock and the estimated fair value of the associated liability related to the redeemable subsidiary preferred shares issued by one of our consolidated subsidiaries were each $1.8 billion. The estimated fair values are based on Level 2 inputs that use pricing models whose inputs are derived primarily from or corroborated by observable market data through correlation or other means for substantially the full term of the financial instrument.
NBCUniversal Media LLC [Member] |
Fair Value, Equity And Cost Method Investments [Line Items] |
Investments | Investments
(in millions) | March 31, 2017 | December 31, 2016
Fair Value Method: |  |  |  |
Snap | $ | 662 |  | $ | — |
Other | 7 |  | 6 |
| 669 |  | 6 |
Equity Method: |  |  |  |
Hulu | 171 |  | 225 |
Other | 400 |  | 336 |
| 571 |  | 561 |
Cost Method: |  |  |  |
BuzzFeed | 400 |  | 400 |
Other | 300 |  | 296 |
| 700 |  | 696 |
Total investments | $ | 1,940 |  | $ | 1,263 |
Fair Value Method Snap In March 2017, Comcast acquired an interest in Snap Inc. as part of its initial public offering. On March 31, 2017, Comcast contributed its investment in Snap to us as an equity contribution which was recorded in our condensed consolidated statement of equity based on the fair value of the investment as of March 31, 2017. We have classified our investment as available for sale. Snap is a camera company whose primary product is Snapchat, a camera app that was created to help people communicate through short videos and images. Equity Method The Weather Channel In January 2016, following a legal restructuring at The Weather Channel, we and the other investors sold the entity holding The Weather Channel’s product and technology businesses to IBM. Following the close of the transaction, we continue to hold an investment in The Weather Channel cable network through a new holding company. As a result of the sale of our investment, we recognized a pretax gain of $108 million in other income (expense), net for the three months ended March 31, 2016.

X
- Definition [Line Items] for Fair Value, Equity And Cost Method Investments [Table] + References No definition available. + Details
Name: | cmcsa_FairValueEquityAndCostMethodInvestmentsLineItems
Namespace Prefix: | cmcsa_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The entire disclosure for investments in certain debt and equity securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -Glossary Debt Security -URI http://asc.fasb.org/extlink&oid=6509901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27290-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -Glossary Equity Security -URI http://asc.fasb.org/extlink&oid=6511694 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 320 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27357-111563 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27405-111563 + Details
Name: | us-gaap_InvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=cmcsa_NBCUniversalMediaLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |