Derivative Instruments (Location and Amounts of Unrealized And Realized Gains (Losses) On Derivatives Recorded In The Condensed Consolidated Income Statements) (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Realized and unrealized gains (losses) on derivatives	$ (19,722)	$ 4,057	$ (23,591)	$ (25,049)
Foreign exchange gain (loss)
Derivative Instruments, Gain (Loss) [Line Items]
Realized and unrealized gains (losses) on derivatives	183	1,886	(5,975)	(580)
Foreign exchange gain (loss) | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Realized and unrealized gains (losses) on derivatives	183	1,886	(5,975)	(580)
Net realized investment gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Realized and unrealized gains (losses) on derivatives	(19,905)	2,171	(17,616)	(24,469)
Net realized investment gains (losses) | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Realized and unrealized gains (losses) on derivatives	134	1,701	928	857
Net realized investment gains (losses) | Interest rate futures and swaps
Derivative Instruments, Gain (Loss) [Line Items]
Realized and unrealized gains (losses) on derivatives	$ (20,039)	$ 470	$ (18,544)	$ (25,326)