Investments - Analysis of net investment income (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Investment Income [Line Items]
Equity securities and other investments	$ 28,200	$ 42,252	$ 35,388
Funds withheld	10,835	14,583	12,783
Total gross investment income	952,685	996,374	1,030,446
Investment expenses	(80,315)	(77,749)	(72,730)
Net investment income	872,370	918,625	957,716
Exclude Life Funds Withheld Assets [Member]
Net Investment Income [Line Items]
Fixed maturities, short term investments and cash equivalents	726,161	809,964	982,275
Net investment income	684,881	789,050	957,716
Life Funds Withheld Assets [Member]
Net Investment Income [Line Items]
Fixed maturities, short term investments and cash equivalents	187,489	129,575	0
Net investment income	$ 187,489	$ 129,575	$ 0

Amount of dividend income on nonoperating securities.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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+ Details

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Amount before accretion (amortization) of purchase discount (premium) of interest income and dividend income on nonoperating securities.

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Amount of expenses related to the generation of investment income.

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Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7(a),(b))
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Income derived from investments in funds withheld distribution of earnings to shareholders by the investee companies.

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