Derivative Instruments (Cash Flow Hedges) (Details) (Interest Rate Swaps, USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivatives In Cash Flow Hedging Relationships [Line Items]
Gains Losses Deferred In Accumulated Other Comprehensive Income Loss On Derivatives Effective Portion	$ 2,583	$ (2,831)	$ (2,352)	$ (2,044)
Investment Related Gains Losses [Member]
Derivatives In Cash Flow Hedging Relationships [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	0	0
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	(3)	(3)	11	0
Investment Income [Member]
Derivatives In Cash Flow Hedging Relationships [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	291	351	796	1,029
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	$ 0	$ 0	$ 0	$ 0