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Fair Value Of Financial Instruments (Quantitative Information related To The Significant Unobservable Inputs Utilized In Company's Level 3 Recurring Fair Value Measurements) (Details) - Discounted Cash Flow [Member] | 12 Months Ended
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Dec. 31, 2017
Auction Rate Equity Securities [Member] |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Workout period range, low end | 1 year
Workout period range, high end | 3 years
Discount rate, weighted average | 4.80%
Weighted average workout period | 2 years 2 months 12 days
Auction Rate Equity Securities [Member] | Minimum [Member] |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Discount rate range | 0.80%
Auction Rate Equity Securities [Member] | Maximum [Member] |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Discount rate range | 9.80%
Auction Rate Municipal Securities [Member] |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Workout period range, low end | 1 year
Workout period range, high end | 4 years
Discount rate, weighted average | 3.40%
Weighted average workout period | 1 year 10 months 24 days
Auction Rate Municipal Securities [Member] | Minimum [Member] |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Discount rate range | 1.00%
Auction Rate Municipal Securities [Member] | Maximum [Member] |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Discount rate range | 9.10%

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- Definition The discount rate used to reduce the estimated amount of loss reserves on short-duration contracts to present value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65670685&loc=d3e14881-158438 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.N.Q1) -URI http://asc.fasb.org/extlink&oid=27015749&loc=d3e569934-122904 + Details
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- Definition The average discount rate applied to insurance contracts to determine future policy benefits to be paid to or on behalf of policyholders. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65670685&loc=d3e14881-158438 + Details
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