Marketable Securities (Available for Sale Securities Measured at Estimated Fair Value on Recurring Basis) (Details) (USD $) | Sep. 28, 2013 | Dec. 29, 2012 |
In Thousands, unless otherwise specified |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | $1,728,397 | $1,641,395 |
Fair Value, Measurements, Recurring [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 1,728,397 | 1,641,395 |
Fair Value, Measurements, Recurring [Member] | Mortgage-Backed Securities [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 518,840 | 650,895 |
Fair Value, Measurements, Recurring [Member] | Obligations of States and Political Subdivisions [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 690,615 | 499,857 |
Fair Value, Measurements, Recurring [Member] | Corporate Bond Securities [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 420,345 | 399,941 |
Fair Value, Measurements, Recurring [Member] | Common Stock [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 27,435 | 22,982 |
Fair Value, Measurements, Recurring [Member] | Other securities [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 71,162 | 67,720 |
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 27,435 | 22,982 |
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Mortgage-Backed Securities [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Obligations of States and Political Subdivisions [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate Bond Securities [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Common Stock [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 27,435 | 22,982 |
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other securities [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 1,700,962 | 1,618,413 |
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Mortgage-Backed Securities [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 518,840 | 650,895 |
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Obligations of States and Political Subdivisions [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 690,615 | 499,857 |
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate Bond Securities [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 420,345 | 399,941 |
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Common Stock [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other securities [Member] | | |
Schedule of Available-for-sale Securities [Line Items] | | |
Available-for-sale Securities, Total | $71,162 | $67,720 |