Claim and Claim Adjustment Expense Reserves (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Claim and Claim Adjustment Expense Reserves [Abstract]
Catastrophe losses net of reinsurance	$ 65	$ 68	$ 104	$ 96