Investments (Details 20) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Equity securities available-for-sale with a gross unrealized loss of 20% or more
% A Rated or Better	20.00%
20% or more [Member] | Twelve months or greater [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	$ 16	$ 7
Equity Securities [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	28	57
Equity Securities [Member] | 20% or more [Member] | Less than six months [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	2
Equity Securities [Member] | 20% or more [Member] | Six months or greater but less than twelve months [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	7
Equity Securities [Member] | 20% or more [Member] | Twelve months or greater [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	16
Equity Securities [Member] | 20% or more [Member] | All Equity Securities With Gross Unrealized Loss Of Twenty Percent Or More [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	25
Non-redeemable preferred stock [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	24	44
Non-redeemable preferred stock [Member] | 20% or more [Member] | Less than six months [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	1
% of All Equity Securities	50.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | Less than six months [Member] | All Industries [Member] | Investment Grade [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	1
% of All Non-Redeemable Preferred Stock	100.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | Less than six months [Member] | Financial Services Industry [Member] | Investment Grade [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	1
% of All Industries	100.00%
% A Rated or Better	100.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | Six months or greater but less than twelve months [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	7
% of All Equity Securities	100.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | Six months or greater but less than twelve months [Member] | All Industries [Member] | Investment Grade [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	1
% of All Non-Redeemable Preferred Stock	14.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | Six months or greater but less than twelve months [Member] | Financial Services Industry [Member] | Investment Grade [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	1
% of All Industries	100.00%
% A Rated or Better	100.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | Twelve months or greater [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	16
% of All Equity Securities	100.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | Twelve months or greater [Member] | Investment Grade [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	15
Non-redeemable preferred stock [Member] | 20% or more [Member] | Twelve months or greater [Member] | All Industries [Member] | Investment Grade [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	15
% of All Non-Redeemable Preferred Stock	94.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | Twelve months or greater [Member] | Financial Services Industry [Member] | Investment Grade [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	15
% of All Industries	100.00%
% A Rated or Better	67.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | All Equity Securities With Gross Unrealized Loss Of Twenty Percent Or More [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	24
% of All Equity Securities	96.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | All Equity Securities With Gross Unrealized Loss Of Twenty Percent Or More [Member] | All Industries [Member] | Investment Grade [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	17
% of All Non-Redeemable Preferred Stock	71.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | All Equity Securities With Gross Unrealized Loss Of Twenty Percent Or More [Member] | Financial Services Industry [Member] | Investment Grade [Member]
Equity securities available-for-sale with a gross unrealized loss of 20% or more
Gross Unrealized Loss	$ 17
% of All Industries	100.00%
% A Rated or Better	71.00%