Fair Value - Change in fair value option table (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	$ (472,495)	$ 230,104	$ (442,597)
Fixed maturities and short term investments [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	(276,776)	228,781	(525,787)
Equities
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	(187,561)	2,605	118,010
Other invested assets [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	(1,835)	(2,664)	(6,970)
Funds Held - Directly Managed [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	$ (6,323)	$ 1,382	$ (27,850)