Investments (Investment Income) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments [Line Items]
Total investment income	$ 141,483	$ 130,097	$ 127,676
Less: Investment expense	(5,645)	(5,167)	(5,805)
Net investment income	135,838	124,930	121,871
Fixed Maturity Securities [Member]
Investments [Line Items]
Total investment income	102,198	102,790	104,111
Equity Securities [Member]
Investments [Line Items]
Total investment income	30,496	18,554	14,629
Short-term Investments [Member]
Investments [Line Items]
Total investment income	$ 8,789	$ 8,753	$ 8,936

Represents the total of interest and dividend income, including any amortization and accretion (as applicable) of discounts and premiums, earned from (1) loans and leases whether held-for-sale or held-in-portfolio; (2) investment securities; (3) federal funds sold; (4) securities purchased under agreements to resell; (5) investments in banker's acceptances, commercial paper, or certificates of deposit; (6) dividend income; or (7) other investments not otherwise specified herein.

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-SubTopic 220
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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