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Commitments and Contingencies (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
NBCUniversal Enterprise [Member]
Commitments And Contingencies [Line Items]
Cash payments for the redemption of redeemable subsidiary preferred stock	$ 725

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- Definition

[Line Items] for Commitment And Contingencies [Table]

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- Definition

Payments For Repurchase Of Redeemable Subsidiary Preferred Stock

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Period Type:	duration

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Namespace Prefix:
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Balance Type:
Period Type: