Investments Available for Sale Securities Reconciliation (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 29, 2019	Dec. 29, 2018
Debt Securities, Available-for-sale [Line Items]
Cost	$ 4,999,522	$ 3,944,459
Debt Securities, Available-for-sale, Unrealized Gain	100,467	2,441
Debt Securities, Available-for-sale, Unrealized Loss	8,013	68,190
Debt Securities, Available-for-sale	5,091,976	3,878,710
Nontaxable Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	1,019,864	1,256,673
Debt Securities, Available-for-sale, Unrealized Gain	1,746	184
Debt Securities, Available-for-sale, Unrealized Loss	1,359	12,759
Debt Securities, Available-for-sale	1,020,251	1,244,098
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	3,809,977	2,527,468
Debt Securities, Available-for-sale, Unrealized Gain	89,836	1,737
Debt Securities, Available-for-sale, Unrealized Loss	6,654	55,085
Debt Securities, Available-for-sale	3,893,159	2,474,120
Debt Securities, Restricted [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	169,681	160,318
Debt Securities, Available-for-sale, Unrealized Gain	8,885	520
Debt Securities, Available-for-sale, Unrealized Loss	0	346
Debt Securities, Available-for-sale	$ 178,566	$ 160,492

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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