Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cumulative effect of accounting changes, net of tax			$ (101)
Postretirement plans:
Amortization of prior service cost	(1)	0
Amortization of actuarial loss	(6)	(4)
Net actuarial (loss) gain during year	69	9
Losses due to plan changes during year	1	1
Postretirement benefits, gross	63	6
Change in other comprehensive (loss) income , net of tax	(61)	91	516
Indemnity
Cumulative effect of accounting changes, net of tax			(6)
Unrealized (loss) gain on securities:
Gross unrealized holding (losses) gains on investments arising during period	(11)	18	105
Unrealized gains transferred to the noncontrolling interest		(23)
Reclassification adjustment for gross (gains) losses included in net income	(5)	(5)	10
Unrealized holding (losses) gains on investments	(16)	(10)	115
Income tax benefit (expense) related to unrealized (losses) gains	5	4	(40)
Net unrealized holding (losses) gains on investment arising during year	(11)	(6)	75
Postretirement plans:
Amortization of prior service cost	1	0	0
Amortization of actuarial loss	6	4	3
Net actuarial (loss) gain during year	(69)	(9)	38
Losses due to plan changes during year	(1)	(1)	(3)
Curtailment/settlement loss arising during year	0	0	(1)
Postretirement benefits, gross	(63)	(6)	37
Income tax benefit (expense) related to postretirement benefits	22	2	(13)
Postretirement plans, net	(41)	(4)	24
Change in other comprehensive (loss) income , net of tax	(52)	(10)	93
Exchange
Postretirement plans:
Change in other comprehensive (loss) income , net of tax	$ (9)	$ 101	$ 423