Benefit Plans - Sirius XM Holdings Inc. Deferred Compensation Plan (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Retirement Benefits [Abstract]
Deferred compensation contributions	$ 3	$ 6
Fair value of investment assets related to deferred compensation plan	50		$ 46
Gains (losses) on investments	$ 1	$ (5)

Carrying amount as of the balance sheet date of assets held under deferred compensation agreements.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Name:	us-gaap_DeferredCompensationPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant