Fair Value Measurement - Level 3 Assets (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	$ 15,257	$ 22,875
Total gains (losses) realized and unrealized:
Included in other comprehensive income	586	(393)
Purchases	17,153	5,196
Sales	(7,249)	(5,896)
Transfers in	2,818	6,640
Transfers out	(10,078)	(12,570)
Ending Balance	17,820	15,257
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0
State and municipal bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	0	5,025
Total gains (losses) realized and unrealized:
Included in other comprehensive income	0	(459)
Purchases	0	0
Sales	(410)	0
Transfers in	900	0
Transfers out	0	(4,566)
Ending Balance		0
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0
Corporate Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	14,500	13,081
Total gains (losses) realized and unrealized:
Included in other comprehensive income	531	73
Purchases	8,900	1,996
Sales	(3,837)	(1,896)
Transfers in	0	6,640
Transfers out	(5,116)	(5,049)
Ending Balance	14,810	14,500
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0
Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	757	4,769
Total gains (losses) realized and unrealized:
Included in other comprehensive income	8	(7)
Purchases	6,500	1,500
Sales	(1,452)	(4,000)
Transfers in	1,000	0
Transfers out	(3,806)	(1,494)
Ending Balance	3,007	757
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0
All other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	0	0
Total gains (losses) realized and unrealized:
Included in other comprehensive income	47	0
Purchases	1,753	1,700
Sales	(1,550)	0
Transfers in	918	0
Transfers out	(1,156)	(1,461)
Ending Balance	3	0
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0
Net investment income
Total gains (losses) realized and unrealized:
Included in earnings	(102)	18
Net investment income \| State and municipal bonds
Total gains (losses) realized and unrealized:
Included in earnings	0	0
Net investment income \| Corporate Debt
Total gains (losses) realized and unrealized:
Included in earnings	(93)	18
Net investment income \| Asset-backed Securities
Total gains (losses) realized and unrealized:
Included in earnings	0	0
Net investment income \| All other investments
Total gains (losses) realized and unrealized:
Included in earnings	(9)	0
Equity in earnings of unconsolidated subsidiaries
Total gains (losses) realized and unrealized:
Included in earnings		(83)
Equity in earnings of unconsolidated subsidiaries \| State and municipal bonds
Total gains (losses) realized and unrealized:
Included in earnings	0	0
Equity in earnings of unconsolidated subsidiaries \| Corporate Debt
Total gains (losses) realized and unrealized:
Included in earnings	0	0
Equity in earnings of unconsolidated subsidiaries \| Asset-backed Securities
Total gains (losses) realized and unrealized:
Included in earnings	0	0
Equity in earnings of unconsolidated subsidiaries \| All other investments
Total gains (losses) realized and unrealized:
Included in earnings	0	(83)
Net realized investment gains (losses)
Total gains (losses) realized and unrealized:
Included in earnings	(565)	(530)
Net realized investment gains (losses) \| State and municipal bonds
Total gains (losses) realized and unrealized:
Included in earnings	(490)	0
Net realized investment gains (losses) \| Corporate Debt
Total gains (losses) realized and unrealized:
Included in earnings	(75)	(363)
Net realized investment gains (losses) \| Asset-backed Securities
Total gains (losses) realized and unrealized:
Included in earnings	0	(11)
Net realized investment gains (losses) \| All other investments
Total gains (losses) realized and unrealized:
Included in earnings	$ 0	$ (156)

Total gains (losses) realized and unrealized.

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Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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

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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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