Observable Input, Constant Maturity Term

No definition available.

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- Definition

Preferred Stock Term

+ References

No definition available.

+ Details

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- Definition

Public equity portfolio fair value disclosure.

+ References

No definition available.

+ Details

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

No definition available.

+ Details

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Period Type:	instant

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Definition

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

Fair value portion of other assets.

+ References

No definition available.

+ Details

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- Definition

The percentage rate used to calculate dividend payments on preferred stock.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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Fair Value (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
Fair Value (Narrative) (Details) - USD ($)	Dec. 31, 2015	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of public equity portfolio		$ 151,699,000		$ 124,228,000
Annual dividend rate	1.75%
Transfers between Level 1 and Level 2		0
Investments within other invested assets		1,767,963,000		1,717,336,000
Market Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfers from level 3		(2,458,000)
Market Value [Member] \| Fixed Maturities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities		374,476,000		383,994,000
Market Value [Member] \| Fixed Maturities [Member] \| Investment Managers' Valuation Committees, Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities		360,518,000		354,133,000
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfers from level 3
Fair Value [Member] \| Fixed Maturities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities		2,350,000		2,337,000
Fair Value [Member] \| Fixed Maturities [Member] \| Investment Managers' Valuation Committees, Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities		$ 2,350,000		2,337,000
Fair Value [Member] \| Fixed Maturities [Member] \| Non-Binding Broker Quote [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities				1,153,000
Redeemable Convertible Preferred Stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Preferred stock tern		25 years
Annual dividend rate		1.75%
Adjustments for New Accounting Pronouncement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments within other invested assets		$ 146,522,000		117,662,000
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments within other invested assets
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments within other invested assets		1,767,963,000		1,717,336,000
Fair Value, Inputs, Level 3 [Member] \| Fair Value [Member] \| Fixed Maturities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities		$ 13,958,000		$ 28,708,000
Senior Notes [Member] \| Senior Notes 4.868% [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Observable input constant maturity		20 years
Debt maturity term		30 years
Debt instrument, stated interest rate		4.868%
Date Due		Jun. 01, 2044		Jun. 01, 2044