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 instruments, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	$ (38,110)	$ 10,759	$ (4,357)
Foreign exchange gain (loss)
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	897	1,274	(749)
Foreign exchange gain (loss) | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	897	1,274	(749)
Net realized investment gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	(39,007)	9,485	(3,608)
Net realized investment gains (losses) | Put options
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	494	(3,822)	(2,222)
Net realized investment gains (losses) | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	3,538	3,054	(1,024)
Net realized investment gains (losses) | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	(45,427)	5,591	0
Net realized investment gains (losses) | Interest rate futures
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	$ 2,388	$ 4,662	$ (362)