Available for Sale Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 28, 2015	Dec. 27, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 6,727,909	$ 6,038,460
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	189,744	211,958
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	18,082	19,688
Fair Value	6,899,571us-gaap_AvailableForSaleSecurities	6,230,730us-gaap_AvailableForSaleSecurities
Tax exempt bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,358,175	3,205,647
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	18,210	17,460
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	3,638	4,011
Fair Value	3,372,747	3,219,096
Taxable bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,923,064	1,569,828
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	5,736	3,005
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1,673	4,592
Fair Value	1,927,127	1,568,241
Restricted investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	170,000	170,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1,121	776
Fair Value	168,879	169,224
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,276,670	1,092,985
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	165,798	191,493
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	11,650	10,309
Fair Value	$ 1,430,818	$ 1,274,169

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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