v3.7.0.1
Condensed Consolidating Financial Information (Condensed Consolidating Statement of Cash Flows) (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Net Cash Provided by (Used in) Operating Activities [Abstract]    
Net Cash Provided by (Used in) Operating Activities $ 5,656 $ 5,399
Investing Activities    
Net transactions with affiliates 0 0
Capital expenditures (2,078) (1,885)
Cash paid for intangible assets (416) (378)
Acquisitions and construction of real estate properties (130) (140)
Acquisitions, net of cash acquired (216) (24)
Proceeds from sales of investments 51 110
Purchases of investments (1,062) (448)
Other 57 56
Net Cash Provided by (Used in) Investing Activities (3,794) (2,709)
Financing Activities    
Proceeds from (repayments of) short-term borrowings, net (1,893) (538)
Proceeds from borrowings 3,500 3,323
Repurchases and repayments of debt (1,059) (48)
Repurchases of common stock under repurchase program and employee plans (996) (1,427)
Dividends paid (657) (611)
Issuances of common stock 0 12
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock (72) (77)
Other 36 9
Net Cash Provided by (Used in) Financing Activities (1,141) 643
Cash and Cash Equivalents, Period Increase (Decrease) 721 3,333
Cash and cash equivalents, beginning of period 3,301 2,295
Cash and cash equivalents, end of period 4,022 5,628
Elimination and Consolidation Adjustments [Member]    
Net Cash Provided by (Used in) Operating Activities [Abstract]    
Net Cash Provided by (Used in) Operating Activities 0 0
Investing Activities    
Net transactions with affiliates 0 0
Capital expenditures 0 0
Cash paid for intangible assets 0 0
Acquisitions and construction of real estate properties 0 0
Acquisitions, net of cash acquired 0 0
Proceeds from sales of investments 0 0
Purchases of investments 0 0
Other 0 0
Net Cash Provided by (Used in) Investing Activities 0 0
Financing Activities    
Proceeds from (repayments of) short-term borrowings, net 0 0
Proceeds from borrowings 0 0
Repurchases and repayments of debt 0 0
Repurchases of common stock under repurchase program and employee plans 0 0
Dividends paid 0 0
Issuances of common stock 0 0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock 0 0
Other 0 0
Net Cash Provided by (Used in) Financing Activities 0 0
Cash and Cash Equivalents, Period Increase (Decrease) 0 0
Cash and cash equivalents, beginning of period 0 0
Cash and cash equivalents, end of period 0 0
Comcast Parent [Member]    
Net Cash Provided by (Used in) Operating Activities [Abstract]    
Net Cash Provided by (Used in) Operating Activities (453) (201)
Investing Activities    
Net transactions with affiliates 1,385 (679)
Capital expenditures (1) (3)
Cash paid for intangible assets 0 0
Acquisitions and construction of real estate properties (69) 0
Acquisitions, net of cash acquired 0 0
Proceeds from sales of investments 0 0
Purchases of investments (9) (7)
Other 55 7
Net Cash Provided by (Used in) Investing Activities 1,361 (682)
Financing Activities    
Proceeds from (repayments of) short-term borrowings, net (1,739) (400)
Proceeds from borrowings 3,500 3,323
Repurchases and repayments of debt (1,000) 0
Repurchases of common stock under repurchase program and employee plans (996) (1,427)
Dividends paid (657) (611)
Issuances of common stock 0 12
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock 0 0
Other (16) (14)
Net Cash Provided by (Used in) Financing Activities (908) 883
Cash and Cash Equivalents, Period Increase (Decrease) 0 0
Cash and cash equivalents, beginning of period 0 0
Cash and cash equivalents, end of period 0 0
Comcast Holdings [Member]    
Net Cash Provided by (Used in) Operating Activities [Abstract]    
Net Cash Provided by (Used in) Operating Activities (10) 0
Investing Activities    
Net transactions with affiliates 10 0
Capital expenditures 0 0
Cash paid for intangible assets 0 0
Acquisitions and construction of real estate properties 0 0
Acquisitions, net of cash acquired 0 0
Proceeds from sales of investments 0 0
Purchases of investments 0 0
Other 0 0
Net Cash Provided by (Used in) Investing Activities 10 0
Financing Activities    
Proceeds from (repayments of) short-term borrowings, net 0 0
Proceeds from borrowings 0 0
Repurchases and repayments of debt 0 0
Repurchases of common stock under repurchase program and employee plans 0 0
Dividends paid 0 0
Issuances of common stock 0 0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock 0 0
Other 0 0
Net Cash Provided by (Used in) Financing Activities 0 0
Cash and Cash Equivalents, Period Increase (Decrease) 0 0
Cash and cash equivalents, beginning of period 0 0
Cash and cash equivalents, end of period 0 0
CCCL Parent [Member]    
Net Cash Provided by (Used in) Operating Activities [Abstract]    
Net Cash Provided by (Used in) Operating Activities (168) 78
Investing Activities    
Net transactions with affiliates 168 (78)
Capital expenditures 0 0
Cash paid for intangible assets 0 0
Acquisitions and construction of real estate properties 0 0
Acquisitions, net of cash acquired 0 0
Proceeds from sales of investments 0 0
Purchases of investments 0 0
Other 0 0
Net Cash Provided by (Used in) Investing Activities 168 (78)
Financing Activities    
Proceeds from (repayments of) short-term borrowings, net 0 0
Proceeds from borrowings 0 0
Repurchases and repayments of debt 0 0
Repurchases of common stock under repurchase program and employee plans 0 0
Dividends paid 0 0
Issuances of common stock 0 0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock 0 0
Other 0 0
Net Cash Provided by (Used in) Financing Activities 0 0
Cash and Cash Equivalents, Period Increase (Decrease) 0 0
Cash and cash equivalents, beginning of period 0 0
Cash and cash equivalents, end of period 0 0
NBCUniversal Media Parent [Member]    
Net Cash Provided by (Used in) Operating Activities [Abstract]    
Net Cash Provided by (Used in) Operating Activities (330) (391)
Investing Activities    
Net transactions with affiliates 115 63
Capital expenditures 0 0
Cash paid for intangible assets 0 0
Acquisitions and construction of real estate properties 0 0
Acquisitions, net of cash acquired 0 0
Proceeds from sales of investments 10 101
Purchases of investments (4) 0
Other 0 (5)
Net Cash Provided by (Used in) Investing Activities 121 159
Financing Activities    
Proceeds from (repayments of) short-term borrowings, net 0 0
Proceeds from borrowings 0 0
Repurchases and repayments of debt (3) (4)
Repurchases of common stock under repurchase program and employee plans 0 0
Dividends paid 0 0
Issuances of common stock 0 0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock 0 0
Other 0 0
Net Cash Provided by (Used in) Financing Activities (3) (4)
Cash and Cash Equivalents, Period Increase (Decrease) (212) (236)
Cash and cash equivalents, beginning of period 482 414
Cash and cash equivalents, end of period 270 178
Comcast Non-Guarantor Subsidiaries [Member]    
Net Cash Provided by (Used in) Operating Activities [Abstract]    
Net Cash Provided by (Used in) Operating Activities 6,617 5,913
Investing Activities    
Net transactions with affiliates (1,678) 694
Capital expenditures (2,077) (1,882)
Cash paid for intangible assets (416) (378)
Acquisitions and construction of real estate properties (61) (140)
Acquisitions, net of cash acquired (216) (24)
Proceeds from sales of investments 41 9
Purchases of investments (1,049) (441)
Other 2 54
Net Cash Provided by (Used in) Investing Activities (5,454) (2,108)
Financing Activities    
Proceeds from (repayments of) short-term borrowings, net (154) (138)
Proceeds from borrowings 0 0
Repurchases and repayments of debt (56) (44)
Repurchases of common stock under repurchase program and employee plans 0 0
Dividends paid 0 0
Issuances of common stock 0 0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock (72) (77)
Other 52 23
Net Cash Provided by (Used in) Financing Activities (230) (236)
Cash and Cash Equivalents, Period Increase (Decrease) 933 3,569
Cash and cash equivalents, beginning of period 2,819 1,881
Cash and cash equivalents, end of period $ 3,752 $ 5,450