Derivatives (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2011 investments reportablesegment interestrateswaps	Sep. 30, 2010	Sep. 30, 2011 Interest Rate Swap Hedging Variable Rate Exposure On Trust Preferred Securities 2006-2011 [Member]	Dec. 31, 2010 Interest Rate Swap Hedging Variable Rate Exposure On Trust Preferred Securities 2006-2011 [Member]	Sep. 30, 2010 Interest Rate Swap Hedging Variable Rate Exposure On Trust Preferred Securities 2006-2011 [Member]	Sep. 30, 2011 Interest Rate Swap Hedging Variable Rate Exposure On Trust Preferred Securities 2011-2016 [Member]	Dec. 31, 2010 Interest Rate Swap Hedging Variable Rate Exposure On Trust Preferred Securities 2011-2016 [Member]	Sep. 30, 2010 Interest Rate Swap Hedging Variable Rate Exposure On Trust Preferred Securities 2011-2016 [Member]
Derivative [Line Items]
Number of interest rate swaps	1
Notional amount of interest rate derivatives			$ 115,000	$ 115,000	$ 115,000	$ 115,000	$ 115,000	$ 115,000
Fixed rate payments, interest rate			7.125%			5.50%
Fair value of collateral pledged to secure interest rate contracts	14,665
Incremental interest expense paid to interest rate swap counterparties	$ 3,961	$ 4,374