Investments (Details 20) (USD $) In Millions, unless otherwise specified	Mar. 31, 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	$ 14
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	32
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	98	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	144
Equity Securities [Member]
Equity securities available-for-sale with a gross unrealized loss of 20%or more
Gross Unrealized Loss	177	299
Non-redeemable preferred stock [Member]
Equity securities available-for-sale with a gross unrealized loss of 20%or more
Gross Unrealized Loss	155	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	13
% of All Equity Securities	93.00%
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	2
% of All Non-Redeemable Preferred Stock	15.00%
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	2
% 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	32
% 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	23
% of All Non-Redeemable Preferred Stock	72.00%
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	23
% of All Industries	100.00%
% A Rated or Better	30.00%
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	98
% 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	98
% 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	98
% 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	143
% of All Equity Securities	99.00%
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	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	$ 123
% of All Industries	100.00%
% A Rated or Better	65.00%