Available for Sale Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 27, 2014	Dec. 28, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 6,038,460	$ 5,836,904
Gross Unrealized Gains	211,958	172,348
Gross Unrealized Losses	19,688	17,766
Fair Value	6,230,730us-gaap_AvailableForSaleSecurities	5,991,486us-gaap_AvailableForSaleSecurities
Tax exempt bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,205,647	3,430,028
Gross Unrealized Gains	17,460	25,588
Gross Unrealized Losses	4,011	9,917
Fair Value	3,219,096	3,445,699
Taxable bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,569,828	1,445,901
Gross Unrealized Gains	3,005	7,641
Gross Unrealized Losses	4,592	3,863
Fair Value	1,568,241	1,449,679
Restricted investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	170,000	170,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	776	86
Fair Value	169,224	169,914
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,092,985	790,975
Gross Unrealized Gains	191,493	139,119
Gross Unrealized Losses	10,309	3,900
Fair Value	$ 1,274,169	$ 926,194

Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax

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- Definition

Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax

+ References

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- Definition

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

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-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

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-Name Accounting Standards Codification

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+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

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