| **Fair Value Measurements - Recurring basis Level 3 rollforward (Details 2) - Recurring basis - Level 3 - USD ($) $ in Thousands**                      | 3 Months Ended | 9 Months Ended |
|---------------------------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Recurring Level 3 financial assets and liabilities**                                                                                                  |           |           |   |   |
| Balance at the beginning of the period                                                                                                                  |           | $ 5,096        |   | $ 5,878 |
| Net income (loss)                                                                                                                                       |           | 0              |   | 0 |
| Other comprehensive income (loss)                                                                                                                       |           | (66)           |   | (143) |
| Settlements                                                                                                                                             |           | (207)          |   | (912) |
| Balance at the end of the period                                                                                                                        |           | 4,823          |   | 4,823 |
| Total gains (losses) for the period included in net income attributable to the change in unrealized gains and losses relating to assets and liabilities |           | 0              |   | 0 |
| Fixed maturities available-for-sale, Corporate debt securities                                                                                          |           |           |   |   |
| **Recurring Level 3 financial assets and liabilities**                                                                                                  |           |           |   |   |
| Balance at the beginning of the period                                                                                                                  | $ 15,056       | 5,065          | $ 4,538 | 5,842 |
| Net income (loss)                                                                                                                                       | 0              | 0              | 0 | 0 |
| Other comprehensive income (loss)                                                                                                                       | 245            | (66)           | 720 | (143) |
| Settlements                                                                                                                                             | (594)          | (216)          | (1,787) | (916) |
| Transfers into Level 3                                                                                                                                  |           |           | 11,236 |   |
| Balance at the end of the period                                                                                                                        | 14,707         | 4,783          | 14,707 | 4,783 |
| Total gains (losses) for the period included in net income attributable to the change in unrealized gains and losses relating to assets and liabilities | 0              | 0              | 0 | 0 |
| Fixed maturities available-for-sale, Asset-backed securities                                                                                            |           |           |   |   |
| **Recurring Level 3 financial assets and liabilities**                                                                                                  |           |           |   |   |
| Balance at the beginning of the period                                                                                                                  |           | 31             |   | 36 |
| Net income (loss)                                                                                                                                       |           | 0              |   | 0 |
| Other comprehensive income (loss)                                                                                                                       |           | 0              |   | 0 |
| Settlements                                                                                                                                             |           | 9              |   | 4 |
| Balance at the end of the period                                                                                                                        |           | 40             |   | 40 |
| Total gains (losses) for the period included in net income attributable to the change in unrealized gains and losses relating to assets and liabilities |           | 0              |   | 0 |
| Embedded Derivative Financial Instruments                                                                                                               |           |           |   |   |
| **Recurring Level 3 financial assets and liabilities**                                                                                                  |           |           |   |   |
| Balance at the beginning of the period                                                                                                                  | 30,687         | 2,919          | 11,257 | 6,407 |
| Net income (loss)                                                                                                                                       | 590            | 6,858          | 20,020 | 3,370 |
| Other comprehensive income (loss)                                                                                                                       | 0              | 0              | 0 | 0 |
| Settlements                                                                                                                                             | 0              | 0              | 0 | 0 |
| Transfers into Level 3                                                                                                                                  |           |           | 0 |   |
| Balance at the end of the period                                                                                                                        | 31,277         | 9,777          | 31,277 | 9,777 |
| Total gains (losses) for the period included in net income attributable to the change in unrealized gains and losses relating to assets and liabilities | $ 590          | $ 6,858        | $ 20,020 | $ 3,370 |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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=36462937&loc=d3e19207-110258
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| X                                                                                                                                                                                                                                                                                                                                                                                          |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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=36462937&loc=d3e19207-110258
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of settlement 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=36462937&loc=d3e19207-110258
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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=36462937&loc=d3e19207-110258
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of gain (loss) recognized in other comprehensive income, arising from assets, liabilities and financial instruments classified in shareholders' equity measured at fair value on a recurring basis using unobservable inputs (level 3).
+ References
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