Accumulated Other Comprehensive Earnings (Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 30, 2023	Dec. 31, 2022	Dec. 25, 2021
Accumulated Other Comprehensive Earnings (Losses), Net of Tax [Roll Forward]
Balances at beginning of period	$ (609)	$ (5)	$ 201
Unrealized gain (loss) on debt securities	206	(626)	(201)
Net realized loss (gain) on debt securities reclassified to investment income	0	1	(16)
Adjustment to postretirement benefit obligation	(1)	21	11
Net other comprehensive earnings (losses)	205	(604)	(206)
Balances at end of period	(404)	(609)	(5)
Investments
Accumulated Other Comprehensive Earnings (Losses), Net of Tax [Roll Forward]
Balances at beginning of period	(618)	7	224
Unrealized gain (loss) on debt securities	206	(626)	(201)
Net realized loss (gain) on debt securities reclassified to investment income	0	1	(16)
Net other comprehensive earnings (losses)	206	(625)	(217)
Balances at end of period	(412)	(618)	7
Postretirement Benefit
Accumulated Other Comprehensive Earnings (Losses), Net of Tax [Roll Forward]
Balances at beginning of period	9	(12)	(23)
Adjustment to postretirement benefit obligation	(1)	21	11
Net other comprehensive earnings (losses)	(1)	21	11
Balances at end of period	$ 8	$ 9	$ (12)