Property and Casualty Unpaid Losses and Loss Expenses (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Paid losses and loss expenses related to:
Add: reinsurance recoverable, end of year	$ 172	$ 168
Property and Casualty Group
Reconciliation of property and casualty beginning and ending loss and loss expense reserve balances
Losses and loss expense reserves, beginning of year, – Gross	3,598	3,499	3,584
Less: reinsurance recoverable, beginning of year	154	151	188
Losses and loss expense reserves, beginning of year, – Net	3,444	3,348	3,396
Incurred losses and loss expenses related to:
Current accident year	3,379	3,494	3,616
Prior accident years	(19)	(115)	(272)
Total incurred losses and loss expenses	3,360	3,379	3,344
Paid losses and loss expenses related to:
Current accident year	2,007	2,166	2,360
Prior accident years	1,206	1,117	1,032
Total paid losses and loss expenses	3,213	3,283	3,392
Losses and loss expense reserves, end of year, – Net	3,591	3,444	3,348
Add: reinsurance recoverable, end of year	156	154	151
Losses and loss expense reserves, end of year, – Gross	3,747	3,598	3,499
Interest rate used to discount workers compensation loss reserves (as a percent)	2.50%	2.50%	2.50%
Reduction in unpaid losses and loss expenses as a result of discounting workers compensation loss reserves	85	85	84
Receivables for salvage and subrogation	$ 149	$ 150	$ 145