Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Cash surrender value of life insurance policies	$ 351	$ 820
Expenses related to retirement investment plans	546	458	$ 446
Severance costs	243	203	315
NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expenses related to retirement investment plans	213	201	185
Severance costs	146	108	165
DreamWorks Animation [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Severance costs			61
DreamWorks Animation [Member] \| NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Severance costs			61
Multiemployer Plans, Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer plan contributions	102	97	84
Multiemployer Plans, Pension [Member] \| NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer plan contributions	102	97	84
Multiemployer Plans, Postretirement Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer plan contributions	183	152	136
Multiemployer Plans, Postretirement Benefit [Member] \| NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer plan contributions	183	152	$ 136
Pension Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation	312	338
Pension Plans [Member] \| NBCUniversal Media LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation	$ 312	$ 338

Carrying amount as of the balance sheet date of amounts which could be received based on the terms of the insurance contract upon surrendering life policies owned by the entity.

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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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