Derivative Instruments (Schedule Of Unrealized And Realized Gains (Losses) On Derivatives Recorded In The Consolidated Income Statement) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives instruments unrealized and realized gains (losses)	$ (76,095)	$ (555)	$ 6,904
Investment Portfolio [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives instruments unrealized and realized gains (losses)	(70,090)
Investment Portfolio [Member] | Net Realized Investment Losses [Member] | Put Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives instruments unrealized and realized gains (losses)	(4,125)
Investment Portfolio [Member] | Net Realized Investment Losses [Member] | Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives instruments unrealized and realized gains (losses)	(6,242)
Investment Portfolio [Member] | Net Realized Investment Losses [Member] | Interest Rate Futures [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives instruments unrealized and realized gains (losses)	(59,723)
Operating Activities [Member] | Net Realized Investment Losses [Member] | Treasury Yield Hedge [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives instruments unrealized and realized gains (losses)		(3,958)
Operating Activities [Member] | Foreign Exchange (Losses) Gains [Member] | Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives instruments unrealized and realized gains (losses)	$ (6,005)	$ 3,403	$ 6,904