Schedule II Valuation and Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 221	$ 198	$ 202
Additions Charged to Costs and Expenses	162	317	293
Deductions from Reserves	178	294	297
Balance at End of Year	205	221	198
Allowance for Doubtful Accounts [Member] \| NBCUniversal Media, LLC [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	65	46	34
Additions Charged to Costs and Expenses	11	33	19
Deductions from Reserves	16	14	7
Balance at End of Year	60	65	46
Sales Returns and Allowances [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	375	307	425
Additions Charged to Costs and Expenses	932	811	663
Deductions from Reserves	948	743	781
Balance at End of Year	359	375	307
Sales Returns and Allowances [Member] \| NBCUniversal Media, LLC [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	372	307	425
Additions Charged to Costs and Expenses	930	808	663
Deductions from Reserves	946	743	781
Balance at End of Year	356	372	307
Deferred Tax Valuation Allowance
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	405	355	297
Additions Charged to Costs and Expenses	33	71	61
Deductions from Reserves	63	21	3
Balance at End of Year	375	405	355
Deferred Tax Valuation Allowance \| NBCUniversal Media, LLC [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	60	73	53
Additions Charged to Costs and Expenses	33	8	23
Deductions from Reserves	6	21	3
Balance at End of Year	$ 87	$ 60	$ 73

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 09

-Article 12

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