Redeemable Noncontrolling Interests - MT. Logan RE (Activity For Redeemable Noncontrolling Interests) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests - Mt. Logan Re, beginning of period				$ 421,552					$ 421,552
Net income (loss) attributable to noncontrolling interests	$ (35,093)	$ (19,019)	$ (26,415)	(16,092)	$ (17,140)	$ (26,337)	$ (7,741)	$ (8,089)	96,619	$ 59,307	$ 5,878
Dividends paid on third party investment in redeemable noncontrolling interest									(68,158)	(10,334)
Redeemable noncontrolling interests - Mt. Logan Re, end of period	756,861				421,552				756,861	421,552
Logan Re [Member]
Redeemable Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests - Mt. Logan Re, beginning of period				$ 421,552				$ 93,378	421,552	93,378
Unaffiliated third party investments during period, net									306,848	279,200
Net income (loss) attributable to noncontrolling interests									96,619	59,307
Dividends paid on third party investment in redeemable noncontrolling interest									(68,158)	(10,334)
Redeemable noncontrolling interests - Mt. Logan Re, end of period	$ 756,861				$ 421,552				$ 756,861	$ 421,552	$ 93,378