Consolidated Statements of Comprehensive Earnings - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Statement of Comprehensive Income [Abstract]
Net earnings	$ 2,025,688	$ 1,965,048	$ 1,735,308
Other comprehensive earnings:
Unrealized gain (loss) on available-for-sale (AFS) securities net of income taxes of $11,093, $(27,605) and $37,133 in 2016, 2015 and 2014, respectively	17,615	(43,838)	58,968
Reclassification adjustment for net realized gain on AFS securities net of income taxes of $(12,464), $(26,972) and $(22,571) in 2016, 2015 and 2014, respectively	(19,792)	(42,829)	(35,842)
Adjustment to postretirement benefit obligation net of income taxes of $(418), $2,394 and $(624) in 2016, 2015 and 2014, respectively	(664)	3,801	(991)
Comprehensive earnings	$ 2,022,847	$ 1,882,182	$ 1,757,443