Fair Value Measurements (Summarize Changes in Level 3 Assets and Liabilities) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Fair Value Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Common stocks transferred to Level 3	2	1
Common stocks transferred out of Level 3		1
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 29,948	$ 20,385
Earnings (Losses)	(6,794)	(456)
Other Comprehensive Income (Losses)	61	46
Impairments	0	0
Purchases	17,369	11,523
Sales	(39,915)	(7,353)
Paydowns/Maturities	0	0
Transfers In / Out	14,889	5,803
Ending Balance	15,558	29,948
Trading account securities sold but not yet purchased
Beginning Balance	793	0
Earnings (Losses)	133	(67)
Other Comprehensive Income (Losses)	0	0
Impairments	0	0
Purchases	7,609	860
Sales	(8,535)	0
Paydowns/Maturities	0	0
Transfers In / Out	0	0
Ending Balance	0	793
Level 3 \| Asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	99	172
Earnings (Losses)	(26)	(2)
Other Comprehensive Income (Losses)	61	46
Impairments	0	0
Purchases	0	0
Sales	(134)	(117)
Paydowns/Maturities	0	0
Transfers In / Out	0	0
Ending Balance	0	99
Level 3 \| Fixed maturity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	99	172
Earnings (Losses)	(26)	(2)
Other Comprehensive Income (Losses)	61	46
Impairments	0	0
Purchases	0	0
Sales	(134)	(117)
Paydowns/Maturities	0	0
Transfers In / Out	0	0
Ending Balance	0	99
Level 3 \| Common stocks
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	8,596	9,370
Earnings (Losses)	2,005	(548)
Other Comprehensive Income (Losses)
Impairments	0	0
Purchases	0	0
Sales	(1,548)	(227)
Paydowns/Maturities	0	0
Transfers In / Out	0	1
Ending Balance	9,053	8,596
Level 3 \| Preferred stocks
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3,945	10,843
Earnings (Losses)	(42)	100
Other Comprehensive Income (Losses)	0	0
Impairments	0	0
Purchases	2,602
Sales	0	(6,998)
Paydowns/Maturities	0	0
Transfers In / Out	0	0
Ending Balance	6,505	3,945
Level 3 \| Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	12,541	20,213
Earnings (Losses)	1,963	(448)
Other Comprehensive Income (Losses)	0	0
Impairments	0	0
Purchases	2,602	0
Sales	(1,548)	(7,225)
Paydowns/Maturities	0	0
Transfers In / Out	0	1
Ending Balance	15,558	12,541
Level 3 \| Trading account
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	17,308	0
Earnings (Losses)	(8,731)	(6)
Other Comprehensive Income (Losses)	0	0
Impairments	0	0
Purchases	14,767	11,523
Sales	(38,233)	(11)
Paydowns/Maturities	0	0
Transfers In / Out	14,889	5,802
Ending Balance	$ 0	$ 17,308

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

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Amount of transfers of financial instrument classified as a liability out of level 3 of the fair value hierarchy.

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Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

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Amount of gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3).

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfer of financial instrument classified as an asset into (out of) level 3 of the fair value hierarchy.

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Amount of gain (loss) recognized in income from liability measured at fair value on recurring basis using unobservable input (level 3).

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Amount of gain (loss) recognized in other comprehensive income (OCI) from liability measured at fair value on recurring basis using unobservable input (level 3).

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Amount of purchases of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sales of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of an intangible asset (excluding goodwill) to fair value.

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Fair Value, Impairment of Intangible Assets (Excluding Goodwill)

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