Net Realized and Unrealized Investment Gains (Losses) (Details) (Trading securities [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Net Realized and Unrealized Investment Gains (Losses)
Total net realized and unrealized investment gains (losses)	$ 371,796	$ (160,735)	$ 493,409
Fixed maturities and short term investments [Member]
Schedule of Net Realized and Unrealized Investment Gains (Losses)
Net realized investment gains (losses) on trading securities	120,734	118,575	172,987
Change in net unrealized investment gains (losses)	228,781	(525,787)	186,063
Equities
Schedule of Net Realized and Unrealized Investment Gains (Losses)
Net realized investment gains (losses) on trading securities	98,733	75,217	72,155
Change in net unrealized investment gains (losses)	2,605	118,010	66,253
Other invested assets [Member]
Schedule of Net Realized and Unrealized Investment Gains (Losses)
Net realized investment gains (losses) on trading securities	(20,686)	20,497	(16,691)
Change in net unrealized investment gains (losses)	(58,180)	56,652	(9,568)
Other realized and unrealized investments gains (losses) [Member]
Schedule of Net Realized and Unrealized Investment Gains (Losses)
Net other realized and unrealized investment (losses) gains	(3,624)	(2,107)	5,843
Funds Held - Directly Managed [Member]
Schedule of Net Realized and Unrealized Investment Gains (Losses)
Net realized investment gains (losses) on trading securities	$ 3,433	$ (21,792)	$ 16,367