Derivative Instruments - Components of life retrocession embedded derivative (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Derivative [Line Items]
Net realized and unrealized gains (losses) on derivative instruments	$ (7,069)	$ (3,622)
Life Funds Withheld Assets
Derivative [Line Items]
Net realized and unrealized (gains) losses on life retrocession embedded derivative	(40,220)	(217,896)
Net adjustments related to future policy benefit reserves, net of tax	(12,408)	(22,053)
Net realized and unrealized (gains) losses on derivative instruments - Life Funds Withheld Assets	2,527	3,869
Net realized and unrealized gains (losses) on derivative instruments	(50,101)	(236,080)
Life Funds Withheld Assets \| Interest (income) expense
Derivative [Line Items]
Net realized and unrealized (gains) losses on life retrocession embedded derivative	(34,341)	(43,110)
Life Funds Withheld Assets \| Net realized and unrealized (gains) losses on derivative instruments
Derivative [Line Items]
Net realized and unrealized (gains) losses on life retrocession embedded derivative	(5,949)	(174,932)
Life Funds Withheld Assets \| Other
Derivative [Line Items]
Net realized and unrealized (gains) losses on life retrocession embedded derivative	$ 70	$ 146

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

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Net Increase or Decrease in the fair value of the embedded derivative or group of embedded derivatives included in earnings in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

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Cumulative adjustment to future policy benefit reserve, excluding foreign exchange effects.

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