Fair Value Measurement (Level 3 Assets) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	$ 17,820	$ 15,257
Included in earnings, as a part of:
Included in other comprehensive income	(211)	(78)
Purchases	7,048	5,060
Sales	(1,712)	(848)
Transfers in	898	0
Transfers out	(998)	(6)
Ending Balance	22,819	19,295
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end	0	0
Corporate debt [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	14,810	14,500
Included in earnings, as a part of:
Included in other comprehensive income	(208)	(75)
Purchases	7,048	0
Sales	(1,712)	(681)
Transfers in	0	0
Transfers out	(998)	(6)
Ending Balance	18,914	13,649
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 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	3,007	757
Included in earnings, as a part of:
Included in other comprehensive income	(5)	(2)
Purchases	0	3,500
Sales	0	(167)
Transfers in	0	0
Transfers out	0	0
Ending Balance	3,002	4,088
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 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	3	0
Included in earnings, as a part of:
Included in other comprehensive income	2	(1)
Purchases	0	1,560
Sales	0	0
Transfers in	898	0
Transfers out	0	0
Ending Balance	903	1,558
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 [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	(39)	(15)
Net investment Income [Member] \| Corporate debt [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	(39)	(14)
Net investment Income [Member] \| Asset-backed securities [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	0	0
Net investment Income [Member] \| All other investments [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	0	(1)
Net realized investment gains (losses) [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	13	(75)
Net realized investment gains (losses) [Member] \| Corporate debt [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	13	(75)
Net realized investment gains (losses) [Member] \| Asset-backed securities [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	0	0
Net realized investment gains (losses) [Member] \| All other investments [Member]
Included in earnings, as a part of:
Total gains (losses) realized and unrealized, included in earnings	$ 0	$ 0

Included in Earnings, as a part of.

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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
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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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.

+ References

No definition available.

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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