Cash, Cash Equivalents And Marketable Securities (Narrative) (Details) - USD ($)	3 Months Ended
Mar. 31, 2019	Apr. 01, 2018
Cash, Cash Equivalents And Marketable Securities [Line Items]
Proceeds from sales of available-for-sale securities	$ 83,264,000	$ 63,313,000
Gross gains or losses related to sales of marketable securities	0	0
Net unrealized gains (losses) included in accumulated other comprehensive income, before taxes	88,000	55,000
Contractual maturities of marketable securities within 1 year	27,644,000
Contractual maturities of marketable securities, years 2-5	27,242,000
Contractual maturities of marketable securities, years 6-10	6,503,000
Contractual maturities of marketable securities, after 10 years	$ 36,378,000
Marketable securities liquidation period	7 days
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Reclassification out of AOCI	$ 0	$ 0

Marketable securities liquidation period

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- Definition

Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

+ References

No definition available.

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- Definition

Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after rolling tenth fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

+ References

No definition available.

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Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in rolling sixth through tenth fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

+ References

No definition available.

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Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year through fifth year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

+ References

No definition available.

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- Definition

This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

+ References

No definition available.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

Amount before 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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- Definition

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

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- Definition

Amount of cash inflow from sale, maturity, prepayment and call of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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