v2.4.0.6
Condensed Consolidating Financial Information (Condensed Consolidating Statement of Cash Flows) (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Operating Activities    
Net cash provided by (used in) operating activities $ 4,369 $ 4,393
Investing Activities    
Net transactions with affiliates 0 0
Capital expenditures (1,361) (1,174)
Cash paid for intangible assets (182) (184)
Acquisition of 30 Rockefeller Plaza properties (1,311)  
Proceeds from sales of businesses and investments 74 35
Return of capital from investees 16  
Purchases of investments (88) (62)
Other 89 36
Net cash provided by (used in) investing activities (2,763) (1,349)
Financing Activities    
Proceeds from (repayments of) short-term borrowings, net 491 (407)
Proceeds from borrowings 2,933  
Repurchases and repayments of debt (1,811) (1,125)
Repurchases and retirements of common stock (500) (750)
Dividends paid (429) (304)
Issuances of common stock 13 150
Purchase of NBCUniversal noncontrolling common equity interest (10,747)  
Distributions (to) from noncontrolling interests (49) (58)
Settlement of Station Venture liability (602)  
Other (17) 37
Net cash provided by (used in) financing activities (10,718) (2,457)
Increase (decrease) in cash and cash equivalents (9,112) 587
Cash and cash equivalents, beginning of period 10,951 1,620
Cash and cash equivalents, end of period 1,839 2,207
Comcast [Member]
    
Operating Activities    
Net cash provided by (used in) operating activities (112) (242)
Investing Activities    
Net transactions with affiliates (2,480) 1,639
Capital expenditures   (2)
Cash paid for intangible assets   (1)
Net cash provided by (used in) investing activities (2,480) 1,636
Financing Activities    
Proceeds from (repayments of) short-term borrowings, net 500  
Proceeds from borrowings 2,933  
Repurchases and repayments of debt   (563)
Repurchases and retirements of common stock (500) (750)
Dividends paid (429) (304)
Issuances of common stock 13 150
Distributions (to) from noncontrolling interests   0
Other 75 73
Net cash provided by (used in) financing activities 2,592 (1,394)
Comcast Holdings [Member]
    
Operating Activities    
Net cash provided by (used in) operating activities 3 (9)
Investing Activities    
Net transactions with affiliates (6) 9
Other 3  
Net cash provided by (used in) investing activities (3) 9
CCCL Parent [Member]
    
Operating Activities    
Net cash provided by (used in) operating activities 49 53
Investing Activities    
Net transactions with affiliates 1,665 (53)
Net cash provided by (used in) investing activities 1,665 (53)
Financing Activities    
Repurchases and repayments of debt (1,714)  
Net cash provided by (used in) financing activities (1,714)  
Combined CCHMO Parents [Member]
    
Operating Activities    
Net cash provided by (used in) operating activities (53) (77)
Investing Activities    
Net transactions with affiliates 53 630
Net cash provided by (used in) investing activities 53 630
Financing Activities    
Repurchases and repayments of debt   (553)
Net cash provided by (used in) financing activities   (553)
NBCUniversal Media Parent [Member]
    
Operating Activities    
Net cash provided by (used in) operating activities (227) (301)
Investing Activities    
Net transactions with affiliates (1,251) 742
Purchases of investments (1) (3)
Other (10) (12)
Net cash provided by (used in) investing activities (1,262) 727
Financing Activities    
Proceeds from (repayments of) short-term borrowings, net   (400)
Repurchases and repayments of debt (87)  
Purchase of NBCUniversal noncontrolling common equity interest (3,200)  
Other (40)  
Net cash provided by (used in) financing activities (3,327) (400)
Increase (decrease) in cash and cash equivalents (4,816) 26
Cash and cash equivalents, beginning of period 5,129 238
Cash and cash equivalents, end of period 313 264
Comcast Non-Guarantor Subsidiaries [Member]
    
Operating Activities    
Net cash provided by (used in) operating activities 4,709 4,969
Investing Activities    
Net transactions with affiliates 2,019 (2,967)
Capital expenditures (1,361) (1,172)
Cash paid for intangible assets (182) (183)
Acquisitions, net of cash acquired (1,311)  
Proceeds from sales of businesses and investments 74 35
Return of capital from investees 16  
Purchases of investments (87) (59)
Other 96 48
Net cash provided by (used in) investing activities (736) (4,298)
Financing Activities    
Proceeds from (repayments of) short-term borrowings, net (9) (7)
Repurchases and repayments of debt (10) (9)
Purchase of NBCUniversal noncontrolling common equity interest (7,547)  
Distributions (to) from noncontrolling interests (49) (58)
Settlement of Station Venture liability (602)  
Other (52) (36)
Net cash provided by (used in) financing activities (8,269) (110)
Increase (decrease) in cash and cash equivalents (4,296) 561
Cash and cash equivalents, beginning of period 5,822 1,382
Cash and cash equivalents, end of period $ 1,526 $ 1,943