Investments - Summary of Proceeds and Gains (Losses) Realized on Securities (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Proceeds received from sales of fixed maturities and equity securities
Proceeds received, Fixed maturity securities	$ 118,818	$ 174,944	$ 229,690	$ 257,033
Proceeds received, Equity securities	11,507	6,474	16,996	12,622
Fixed maturity securities
Proceeds received from sales of fixed maturities and equity securities
Gross gains realized	4,080	8,382	6,569	10,858
Gross losses realized	(496)	(948)	(1,377)	(1,440)
Equity securities
Proceeds received from sales of fixed maturities and equity securities
Gross gains realized	1,702	650	2,750	1,170
Gross losses realized	$ (236)	$ (195)	$ (428)	$ (841)

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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
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27357-111563

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

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The cash inflow associated with the sale of debt securities classified as available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26853-111562

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3179-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

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The cash inflow associated with the sale of equity securities classified as available-for-sale securities.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 320
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26853-111562

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-Name Accounting Standards Codification
-Glossary Investing Activities
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