Condensed Consolidating Financial Information (Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Assets
Cash and cash equivalents	$ 2,693	$ 3,301	$ 4,665	$ 2,295
Receivables, net	7,849	7,955
Programming rights	1,633	1,250
Other current assets	2,657	3,855
Total current assets	14,832	16,361
Film and television costs	6,595	7,252
Investments	6,521	5,247
Investments in and amounts due from subsidiaries eliminated upon consolidation	0	0
Property and equipment, net	37,171	36,253
Franchise rights	59,364	59,364
Goodwill	36,742	35,980
Other intangible assets, net	18,907	17,274
Other noncurrent assets, net	2,899	2,769
Total assets	183,031	180,500
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	6,730	6,915
Accrued participations and residuals	1,882	1,726
Accrued expenses and other current liabilities	7,306	7,414
Current portion of long-term debt	6,358	5,480
Total current liabilities	22,276	21,535
Long-term debt, less current portion	57,210	55,566
Deferred income taxes	35,409	34,854
Other noncurrent liabilities	10,837	10,925
Redeemable noncontrolling interests	1,451	1,446
Equity:
Common stock	56	56
Other shareholders’ equity	54,949	53,887
Total Comcast Corporation shareholders’ equity	55,005	53,943
Noncontrolling interests	843	2,231
Total equity	55,848	56,174	55,276	53,978
Total liabilities and equity	183,031	180,500
Elimination and Consolidation Adjustments [Member]
Assets
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	0	0
Total current assets	0	0
Film and television costs	0	0
Investments	0	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	(511,749)	(481,214)
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	(1,026)	(1,017)
Total assets	(512,775)	(482,231)
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities	0	0
Current portion of long-term debt	0	0
Total current liabilities	0	0
Long-term debt, less current portion	0	0
Deferred income taxes	(1,055)	(1,017)
Other noncurrent liabilities	29	0
Redeemable noncontrolling interests	0	0
Equity:
Common stock	0	0
Other shareholders’ equity	(511,749)	(481,214)
Total Comcast Corporation shareholders’ equity	(511,749)	(481,214)
Noncontrolling interests	0	0
Total equity	(511,749)	(481,214)
Total liabilities and equity	(512,775)	(482,231)
Comcast Parent [Member] | Reportable Legal Entities [Member]
Assets
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	67	151
Total current assets	67	151
Film and television costs	0	0
Investments	96	75
Investments in and amounts due from subsidiaries eliminated upon consolidation	101,430	98,350
Property and equipment, net	434	298
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	11	13
Other noncurrent assets, net	1,149	1,138
Total assets	103,187	100,025
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	12	23
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities	1,887	1,726
Current portion of long-term debt	4,032	3,739
Total current liabilities	5,931	5,488
Long-term debt, less current portion	39,725	38,123
Deferred income taxes	0	0
Other noncurrent liabilities	2,526	2,471
Redeemable noncontrolling interests	0	0
Equity:
Common stock	56	56
Other shareholders’ equity	54,949	53,887
Total Comcast Corporation shareholders’ equity	55,005	53,943
Noncontrolling interests	0	0
Total equity	55,005	53,943
Total liabilities and equity	103,187	100,025
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Assets
Cash and cash equivalents	2,383	2,819	4,395	1,881
Receivables, net	7,849	7,955
Programming rights	1,633	1,250
Other current assets	2,569	3,668
Total current assets	14,434	15,692
Film and television costs	6,595	7,252
Investments	5,719	4,521
Investments in and amounts due from subsidiaries eliminated upon consolidation	110,545	97,704
Property and equipment, net	36,737	35,955
Franchise rights	59,364	59,364
Goodwill	36,742	35,980
Other intangible assets, net	18,896	17,261
Other noncurrent assets, net	2,035	1,921
Total assets	291,067	275,650
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	6,718	6,892
Accrued participations and residuals	1,882	1,726
Accrued expenses and other current liabilities	4,746	5,045
Current portion of long-term debt	2,322	1,187
Total current liabilities	15,668	14,850
Long-term debt, less current portion	7,039	6,994
Deferred income taxes	35,886	35,259
Other noncurrent liabilities	7,171	7,288
Redeemable noncontrolling interests	1,451	1,446
Equity:
Common stock	0	0
Other shareholders’ equity	223,009	207,582
Total Comcast Corporation shareholders’ equity	223,009	207,582
Noncontrolling interests	843	2,231
Total equity	223,852	209,813
Total liabilities and equity	291,067	275,650
Comcast Holdings [Member] | Subsidiary Issuer [Member] | Reportable Legal Entities [Member]
Assets
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	0	0
Total current assets	0	0
Film and television costs	0	0
Investments	1	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	126,187	120,071
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	658	638
Total assets	126,846	120,709
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities	92	0
Current portion of long-term debt	0	0
Total current liabilities	92	0
Long-term debt, less current portion	142	141
Deferred income taxes	508	542
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests	0	0
Equity:
Common stock	0	0
Other shareholders’ equity	126,104	120,026
Total Comcast Corporation shareholders’ equity	126,104	120,026
Noncontrolling interests	0	0
Total equity	126,104	120,026
Total liabilities and equity	126,846	120,709
CCCL Parent [Member] | Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Assets
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	0	0
Total current assets	0	0
Film and television costs	0	0
Investments	15	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	124,549	117,696
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	0	0
Total assets	124,564	117,696
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities	295	341
Current portion of long-term debt	0	550
Total current liabilities	295	891
Long-term debt, less current portion	2,100	2,100
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests	0	0
Equity:
Common stock	0	0
Other shareholders’ equity	122,169	114,705
Total Comcast Corporation shareholders’ equity	122,169	114,705
Noncontrolling interests	0	0
Total equity	122,169	114,705
Total liabilities and equity	124,564	117,696
NBCUniversal Media Parent [Member] | Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Assets
Cash and cash equivalents	310	482	$ 270	$ 414
Receivables, net	0	0
Programming rights	0	0
Other current assets	21	36
Total current assets	331	518
Film and television costs	0	0
Investments	690	651
Investments in and amounts due from subsidiaries eliminated upon consolidation	49,038	47,393
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	83	89
Total assets	50,142	48,651
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities	286	302
Current portion of long-term debt	4	4
Total current liabilities	290	306
Long-term debt, less current portion	8,204	8,208
Deferred income taxes	70	70
Other noncurrent liabilities	1,111	1,166
Redeemable noncontrolling interests	0	0
Equity:
Common stock	0	0
Other shareholders’ equity	40,467	38,901
Total Comcast Corporation shareholders’ equity	40,467	38,901
Noncontrolling interests	0	0
Total equity	40,467	38,901
Total liabilities and equity	$ 50,142	$ 48,651