Shareholders' Equity (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accumulated other comprehensive income (loss), net of tax
Pretax Net Unrealized Gains (Losses) on Securities, Beginning Balance	$ 736	$ 258	$ (1,058)
Foreign Currency Translation Adjustment, Beginning Balance	9	1	(18)
Pension and Other Postretirement Plans Adjustment, Beginning Balance	(13)	(13)	(11)
Tax Effects, Beginning Balance	(253)	(86)	374
Non-controlling Interest, Beginning Balance		3	10
Accumulated Other Comprehensive Income (Loss), Beginning Balance	479	163	(703)
Cumulative effect of accounting change on net unrealized gains (losses) on securities, before tax			(27)
Cumulative effect of accounting change, tax			10
Cumulative effect of accounting change, net of tax			(17)
Unrealized holding gains (losses) on securities arising during the year, before tax	238	596	1,413
Unrealized holding gains (losses) on securities arising during the year, tax	(84)	(208)	(490)
Unrealized holding gains (losses) on securities arising during the year, net of tax, attributable to non-controlling interests	(7)	(4)	(9)
Unrealized holding gains (losses) on securities arising during the year, net of tax	147	384	914
Realized gains included in net income, before tax	(105)	(112)	(70)
Realized gains included in net income, tax	37	39	19
Realized gains included in net income, net of tax, attributable to non-controlling interests	2	2	3
Realized gains included in net income, net of tax	(66)	(71)	(48)
Unrealized gains on subsidiary sold, before tax	(2)
Unrealized gains on subsidiary sold, tax	1
Unrealized gains on subsidiary sold, net of tax	(1)
Foreign currency translation gains (losses), before tax	(2)	8	19
Foreign currency translation gains (losses), net of tax, attributable to non-controlling interests	(1)		(1)
Foreign currency translation gains (losses), net of tax	(3)	8	18
Other changes in net unrealized gains (losses) on securities, before tax		(6)
Other changes in pension and other postretirement plans, before tax	1		(2)
Other, tax	0	2	1
Other, net of tax, attributable to non-controlling interests		(1)
Other, net of tax	1	(5)	(1)
Pretax Net Unrealized Gains (Losses) on Securities, Ending Balance	867	736	258
Foreign Currency Translation Adjustment, Ending Balance	7	9	1
Pension and Other Postretirement Plans Adjustment, Ending Balance	(12)	(13)	(13)
Tax Effects, Ending Balance	(299)	(253)	(86)
Non-controlling Interest, Ending Balance	(6)		3
Accumulated Other Comprehensive Income (Loss), Ending Balance	$ 557	$ 479	$ 163