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] | Less than six months [Member]
Equity securities available-for-sale with a gross unrealized loss of 20%or more
Gross Unrealized Loss	$ 28
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	14
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	124	96
20% or more [Member] | All equity securities with a gross unrealized loss of 20% or more [Member]
Equity securities available-for-sale with a gross unrealized loss of 20%or more
Gross Unrealized Loss	166
Equity Securities [Member]
Equity securities available-for-sale with a gross unrealized loss of 20%or more
Gross Unrealized Loss	199	299
Non-redeemable preferred stock [Member]
Equity securities available-for-sale with a gross unrealized loss of 20%or more
Gross Unrealized Loss	157	202
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	7
% of All Equity Securities	25.00%
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	6
% of All Non-Redeemable Preferred Stock	86.00%
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	6
% 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	14
% 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	2
% 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	2
% 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	124
% of All Equity Securities	100.00%
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	115
% of All Non-Redeemable Preferred Stock	93.00%
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	115
% of All Industries	100.00%
% A Rated or Better	72.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | All equity securities with a gross unrealized loss of 20% or more [Member]
Equity securities available-for-sale with a gross unrealized loss of 20%or more
Gross Unrealized Loss	145
% of All Equity Securities	87.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | All equity securities with a gross unrealized loss of 20% 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	123
% of All Non-Redeemable Preferred Stock	85.00%
Non-redeemable preferred stock [Member] | 20% or more [Member] | All equity securities with a gross unrealized loss of 20% or more [Member] | Financial Services Industry [Member]
Equity securities available-for-sale with a gross unrealized loss of 20%or more
Gross Unrealized Loss	0
Non-redeemable preferred stock [Member] | 20% or more [Member] | All equity securities with a gross unrealized loss of 20% 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	$ 123
% of All Industries	100.00%
% A Rated or Better	74.00%