Amortized Cost and Fair Value of Available for Sale Securities by Expected Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 26, 2015
Amortized Cost
Due in one year or less	$ 1,592,144	$ 1,375,450
Due after one year through five years	3,218,371	3,951,600
Due after five years through ten years	680,641	161,732
Due after ten years	14,096	62,425
Available-for-sale Securities, Debt Maturities, Amortized Cost	5,505,252	5,551,207
Amortized cost of available-for-sale securities	6,691,140	6,551,908
Fair Value
Due in one year or less	1,591,740	1,376,698
Due after one year through five years	3,187,739	3,948,654
Due after five years through ten years	656,162	162,999
Due after ten years	14,629	63,250
Available-for-sale Securities, Debt Maturities, Fair Value	5,450,270	5,551,601
Fair value of available-for-sale securities	6,738,618	6,602,934
Restricted investments
Amortized Cost
Amortized cost of available-for-sale securities	164,548	164,548
Fair Value
Fair value of available-for-sale securities	164,085	163,159
Equity securities
Amortized Cost
Amortized cost of available-for-sale securities	1,021,340	836,153
Fair Value
Fair value of available-for-sale securities	$ 1,124,263	$ 888,174