Investments - Schedule of reconciliation of the balances for all investments measured at fair value using significant unobservable inputs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Assets
Asset fair value, beginning balance	$ 12,314	$ 3,857
Transfers in to (out of) Level 3	1,921	6,868
Purchases	1,505	1,653
Sales	(1,903)	0
Realized and Unrealized Gains (Losses)	1,616	2,145
Asset fair value, ending balance	15,453	14,523
Derivative liabilities (embedded)
Assets
Asset fair value, beginning balance		(2,510)
Transfers in to (out of) Level 3		0
Purchases		0
Sales		0
Realized and Unrealized Gains (Losses)		(170)
Asset fair value, ending balance		(2,680)
Liabilities
Liability fair value, beginning balance	(4,430)
Transfers in to (out of) Level 3	0
Purchases	0
Sales	(783)
Realized and Unrealized Gains(Losses) (1)	(143)
Liability fair value, ending balance	(5,356)
Asset-backed securities
Assets
Asset fair value, beginning balance	400
Transfers in to (out of) Level 3	1,921
Purchases	1,364
Sales	(1,903)
Realized and Unrealized Gains (Losses)	1,770
Asset fair value, ending balance	3,552
Bank debt
Assets
Asset fair value, beginning balance		54
Transfers in to (out of) Level 3		(54)
Purchases		0
Sales		0
Realized and Unrealized Gains (Losses)		0
Asset fair value, ending balance		0
Corporate bonds
Assets
Asset fair value, beginning balance	4,610	1,046
Transfers in to (out of) Level 3	0	6,922
Purchases	87	0
Sales	0	0
Realized and Unrealized Gains (Losses)	84	1,386
Asset fair value, ending balance	4,781	9,354
Private common equity securities
Assets
Asset fair value, beginning balance	2,012	2,757
Transfers in to (out of) Level 3	0	0
Purchases	0	1,653
Sales	0	0
Realized and Unrealized Gains (Losses)	0	(4)
Asset fair value, ending balance	2,012	4,406
Derivative assets
Assets
Asset fair value, beginning balance		0
Transfers in to (out of) Level 3		0
Purchases		0
Sales		0
Realized and Unrealized Gains (Losses)		763
Asset fair value, ending balance		763
Investments in limited partnerships
Assets
Asset fair value, beginning balance	5,292
Transfers in to (out of) Level 3	0
Purchases	54
Sales	0
Realized and Unrealized Gains (Losses)	(238)
Asset fair value, ending balance	$ 5,108

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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

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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)

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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

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-Section 50

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- Definition

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

+ References

No definition available.

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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

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- Definition

Amount of gain (loss) recognized on the income statement for financial instrument classified as a liability 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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- Definition

Amount of purchases of financial instrument classified as a liability 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)

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- Definition

Amount of sales of financial instrument classified as a liability 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=25499696&loc=d3e19207-110258

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- Definition

Amount of transfers of financial instrument classified as a liability into (out of) level 3 of the fair value hierarchy.

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No definition available.

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Fair value of financial instrument classified as a liability 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)

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