Investments (Details 20) (USD $) In Millions, unless otherwise specified	Jun. 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	$ 19
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	46
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	100	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	165
Equity Securities [Member]
Equity securities available-for-sale with a gross unrealized loss of 20%or more
Gross Unrealized Loss	221	299
Non-redeemable preferred stock [Member]
Equity securities available-for-sale with a gross unrealized loss of 20%or more
Gross Unrealized Loss	160	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	10
% of All Equity Securities	53.00%
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	7
% of All Non-Redeemable Preferred Stock	70.00%
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	7
% of All Industries	100.00%
% A Rated or Better	86.00%
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	46
% 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	27
% of All Non-Redeemable Preferred Stock	59.00%
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	27
% of All Industries	100.00%
% A Rated or Better	37.00%
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	100
% 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	100
% of All Non-Redeemable Preferred Stock	100.00%
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	100
% of All Industries	100.00%
% A Rated or Better	75.00%
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	156
% of All Equity Securities	95.00%
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	134
% of All Non-Redeemable Preferred Stock	86.00%
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	$ 134
% of All Industries	100.00%
% A Rated or Better	68.00%