Summary of Investments (Net Realized Investment Gains and Losses and Proceeds) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Gain (Loss) on Investments [Line Items]
Total net realized investment gains	$ 2,680	$ 1,596	$ 6,634	$ 3,651
Available-for-sale Securities [Abstract]
Proceeds from sales	0	1,074	5,059	3,042
Gross realized gains	0	54	2,300	975
Gross realized losses	0	0	(78)	0
Fixed maturities: \| Available-for-sale
Gain (Loss) on Investments [Line Items]
Total net realized investment gains	676	846	2,671	1,362
Fixed maturities: \| Change in fair value
Gain (Loss) on Investments [Line Items]
Total net realized investment gains	176	98	547	371
Fixed maturities: \| Sales
Gain (Loss) on Investments [Line Items]
Total net realized investment gains	(11)	461	46	461
Equity securities: \| Available-for-sale
Gain (Loss) on Investments [Line Items]
Total net realized investment gains	1,299	0	2,709	984
Equity securities: \| Change in fair value
Gain (Loss) on Investments [Line Items]
Total net realized investment gains	245	237	356	330
Equity securities: \| Sales
Gain (Loss) on Investments [Line Items]
Total net realized investment gains	6	(26)	16	(26)
Short-term investments
Gain (Loss) on Investments [Line Items]
Total net realized investment gains	0	(43)	0	0
Cash equivalents
Gain (Loss) on Investments [Line Items]
Total net realized investment gains	0	23	0	169
Real estate
Gain (Loss) on Investments [Line Items]
Total net realized investment gains	$ 289	$ 0	$ 289	$ 0

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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
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The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
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