Consolidated Statements of Comprehensive Earnings - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Statement of Comprehensive Income [Abstract]
Net earnings	$ 789,341	$ 574,026	$ 661,057	$ 980,971	$ 406,980	$ 677,744	$ 616,172	$ 680,271	$ 3,005,395	$ 2,381,167	$ 2,291,894
Other comprehensive earnings:
Unrealized gain (loss) on debt securities net of income taxes of $50,504 and $(6,521) in 2019 and 2018, respectively. Unrealized gain on debt and equity securities net of income taxes of $110,818 in 2017.									148,141	(19,126)	175,978
Reclassification adjustment for net realized (gain) loss on debt securities net of income taxes of $(205) and $118 in 2019 and 2018, respectively. Reclassification adjustment for net realized (gain) on debt and equity securities net of income taxes of $(42,088) in 2017.									(602)	346	(66,836)
Adjustment to postretirement benefit obligation net of income taxes of $(3,576), $2,963 and $(4,406) in 2019, 2018 and 2017, respectively.									(10,488)	8,692	(6,997)
Comprehensive earnings									$ 3,142,446	$ 2,371,079	$ 2,394,039