Temporarily Impaired Available for Sale Debt Securities by Time Period Impaired (Details) - USD ($) $ in Thousands	Jun. 26, 2021	Dec. 26, 2020
Debt Securities, Available-for-sale [Line Items]
Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 3,040,119	$ 1,161,091
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	44,059	8,034
Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	64,401	39,622
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	557	378
Unrealized Loss Position, Fair Value	3,104,520	1,200,713
Unrealized Loss Position, Accumulated Loss	44,616	8,412
Tax exempt bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	56,890	3,704
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	17	88
Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	0	0
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Unrealized Loss Position, Fair Value	56,890	3,704
Unrealized Loss Position, Accumulated Loss	17	88
Taxable bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	2,973,436	1,157,387
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	43,941	7,946
Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	64,401	39,622
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	557	378
Unrealized Loss Position, Fair Value	3,037,837	1,197,009
Unrealized Loss Position, Accumulated Loss	44,498	8,324
Restricted investments [Member]
Debt Securities, Available-for-sale [Line Items]
Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	9,793	0
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	101	0
Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	0	0
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Unrealized Loss Position, Fair Value	9,793	0
Unrealized Loss Position, Accumulated Loss	$ 101	$ 0

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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