Accumulated Other Comprehensive Earnings (Details) - USD ($) $ in Thousands	3 Months Ended
Apr. 01, 2017	Mar. 26, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances at Beginning of Period	$ 23,427	$ 26,268
Unrealized gain on AFS securities	38,918	10,965
Net realized gain on AFS securities reclassified to investment income	(19,187)	(3,495)
Net other comprehensive earnings	19,731	7,470
Balances at End of Period	43,158	33,738
AFS Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances at Beginning of Period	29,118	31,295
Unrealized gain on AFS securities	38,918	10,965
Net realized gain on AFS securities reclassified to investment income	(19,187)	(3,495)
Net other comprehensive earnings	19,731	7,470
Balances at End of Period	48,849	38,765
Postretirement Benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances at Beginning of Period	(5,691)	(5,027)
Net other comprehensive earnings	0	0
Balances at End of Period	$ (5,691)	$ (5,027)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount after tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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