Temporarily Impaired Available for Sale Securities by Time Period Impaired (Detail) - USD ($) $ in Thousands	Sep. 26, 2020	Dec. 28, 2019
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 1,449,683	$ 621,777
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	8,034	899
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	297,617
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	674
Debt Securities, Available-for-sale, Unrealized Loss Position	1,449,683	919,394
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	8,034	1,573
Nontaxable Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	29,415	48,462
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	136	11
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	99,976
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	119
Debt Securities, Available-for-sale, Unrealized Loss Position	29,415	148,438
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	136	130
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,420,268	573,315
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	7,898	888
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	197,641
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	555
Debt Securities, Available-for-sale, Unrealized Loss Position	1,420,268	770,956
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 7,898	$ 1,443

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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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