Equity Securities and Indexed Debt Securities (ZENS) - Schedule of Securities Classified as Trading (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Debt and Equity Securities, FV-NI [Line Items]
Carrying Value	$ 555	$ 510
AT&T Common
Debt and Equity Securities, FV-NI [Line Items]
Balance of investment owned (in shares)	10,212,945	10,212,945
Carrying Value	$ 296	$ 254
Charter Common
Debt and Equity Securities, FV-NI [Line Items]
Balance of investment owned (in shares)	872,503	872,503
Carrying Value	$ 188	$ 182
WBD Common
Debt and Equity Securities, FV-NI [Line Items]
Balance of investment owned (in shares)	2,470,685	2,470,685
Carrying Value	$ 68	$ 71
Other
Debt and Equity Securities, FV-NI [Line Items]
Carrying Value	$ 3	$ 3