Reconciliation of Shareholders' Equity (Details) (USD $) In Millions, except Per Share data	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Reconciliation of shareholders' equity
Balance at the beginning of the period			$ 6,334	$ 5,725	$ 5,725
Comprehensive income:
Net income	(107)	(31)	167	131	660
Other comprehensive income, net of tax:
Unrealized (loss) gains on securities			22		110
Reclassification of unrealized gain on sale of affiliated subsidiaries			(9)		(15)
Postretirement plans:
Amortization of prior service cost					0
Amortization of net actuarial loss					2
Net actuarial loss during year					(6)
Loss due to plan changes during year					0
Curtailment/settlement loss arising during year					0
Postretirement plans					(4)
Other comprehensive (loss) income, net of tax	17	31	13	82	91
Reclassification of unrealized gain on sale of affiliated subsidiaries			9		15
Comprehensive income	(90)	0	189	213	766
Purchase of treasury stock			(90)		(58)
Dividends declared:
Balance at the end of the period	6,382		6,382		6,334
Class A | Indemnity
Dividends declared:
Dividends declared (in dollars per share)	$ 0.515	$ 0.48	$ 1.03	$ 0.96	$ 1.995
Total dividends declared			(51)		(99)
Class B | Indemnity
Dividends declared:
Dividends declared (in dollars per share)	$ 77.25	$ 72.00	$ 154.500	$ 144.000	$ 293.250
Total dividends declared			0		0
Indemnity
Reconciliation of shareholders' equity
Balance at the beginning of the period			912	902	902
Comprehensive income:
Net income	52	49	96	96	162
Other comprehensive income, net of tax:
Unrealized (loss) gains on securities			(1)		9
Reclassification of unrealized gain on sale of affiliated subsidiaries			(9)		(15)
Postretirement plans:
Amortization of prior service cost					0
Amortization of net actuarial loss					2
Net actuarial loss during year					(6)
Loss due to plan changes during year					0
Curtailment/settlement loss arising during year					0
Postretirement plans					(4)
Other comprehensive (loss) income, net of tax	0	5	(10)	11	(10)
Reclassification of unrealized gain on sale of affiliated subsidiaries			9		15
Comprehensive income	52	54	95	107	167
Purchase of treasury stock			(90)		(58)
Dividends declared:
Balance at the end of the period	866		866		912
Exchange
Reconciliation of shareholders' equity
Balance at the beginning of the period			5,422	4,823	4,823
Comprehensive income:
Net income			71		498
Other comprehensive income, net of tax:
Unrealized (loss) gains on securities			23		101
Postretirement plans:
Other comprehensive (loss) income, net of tax	17	26	23	71	101
Comprehensive income	142	54	94	(106)	599
Dividends declared:
Balance at the end of the period	5,516		5,516		5,422
Class A
Dividends declared:
Total dividends declared			(51)		(99)
Class B
Dividends declared:
Total dividends declared			$ 0		$ 0