Net Investment Income (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net Investment Income [Line Items]
Investment Income	$ 26,453	$ 23,515	$ 76,279	$ 69,018
Investment Expenses	(802)	(917)	(2,325)	(2,707)
Net Investment Income	25,651	22,598	73,954	66,311
Fixed Maturities
Net Investment Income [Line Items]
Investment Income	22,733	19,491	65,504	57,019
Equity Securities
Net Investment Income [Line Items]
Investment Income	3,052	3,774	9,138	11,337
Short-Term Investments, Cash & Cash Equivalents
Net Investment Income [Line Items]
Investment Income	509	84	1,151	254
Other Invested Assets
Net Investment Income [Line Items]
Investment Income	$ 159	$ 166	$ 486	$ 408

Amount, before investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

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Amount of expenses related to the generation of investment income.

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Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

+ References

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