Fair Value Of Financial Instruments (Quantitative Information related To The Significant Unobservable Inputs Utilized In Company's Level 3 Recurring Fair Value Measurements) (Details)	3 Months Ended
Mar. 31, 2017
Market Comparable Companies [Member] \| Corporate Equity Securities [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Tangible book value multiple, weighted average	1.9
Market Comparable Companies [Member] \| Corporate Equity Securities [Member] \| Minimum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Tangible book value multiple range	1.4
Market Comparable Companies [Member] \| Corporate Equity Securities [Member] \| Maximum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Tangible book value multiple range	2.2
Discounted Cash Flow [Member] \| 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	5.80%
Weighted average workout period	2 years 6 months
Discounted Cash Flow [Member] \| Auction Rate Equity Securities [Member] \| Minimum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate range	1.60%
Discounted Cash Flow [Member] \| Auction Rate Equity Securities [Member] \| Maximum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate range	11.50%
Discounted Cash Flow [Member] \| 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	4.40%
Weighted average workout period	1 year 10 months 24 days
Discounted Cash Flow [Member] \| Auction Rate Municipal Securities [Member] \| Minimum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate range	1.90%
Discounted Cash Flow [Member] \| Auction Rate Municipal Securities [Member] \| Maximum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate range	10.10%

Fair value inputs tangible book value multiple.

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Weighted average tangible book value multiple.

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Weighted average workout period.

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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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- 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

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The average discount rate applied to insurance contracts to determine future policy benefits to be paid to or on behalf of policyholders.

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