Available for Sale Debt Securities Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 27, 2021	Dec. 26, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 8,977,750	$ 8,898,168
Unrealized Gains	213,043	308,536
Unrealized Losses	59,241	8,412
Fair Value	9,131,552	9,198,292
Tax exempt bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	494,115	548,438
Unrealized Gains	5,776	7,408
Unrealized Losses	47	88
Fair Value	499,844	555,758
Taxable bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,315,795	8,182,003
Unrealized Gains	194,900	286,745
Unrealized Losses	59,194	8,324
Fair Value	8,451,501	8,460,424
Restricted investments [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	167,840	167,727
Unrealized Gains	12,367	14,383
Unrealized Losses	0	0
Fair Value	$ 180,207	$ 182,110

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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