CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Cash and cash equivalents	$ 404	$ 185
Other assets	563	441
Indemnity
Fixed maturities, amortized cost	531	535
Equity securities, cost	27	24
Trading securities, cost	24	23
Limited partnerships, cost	171	185
Cash and cash equivalents	12	11
Other assets	115	119
Treasury stock (in shares)	21,171,682	20,427,758
Exchange
Fixed maturities, amortized cost	6,909	6,829
Equity securities, cost	543	531
Trading securities, cost	2,104	2,021
Limited partnerships, cost	976	1,003
Cash and cash equivalents	392	174
Other assets	$ 448	$ 322
Class A | Indemnity
Common stock, stated value per share (in dollars per share)	$ 0.0292	$ 0.0292
Common stock, authorized (in shares)	74,996,930	74,996,930
Common stock, issued (in shares)	68,294,400	68,289,600
Common stock, outstanding (in shares)	47,122,718	47,861,842
Class B | Indemnity
Ratio for converting shares of Class B common stock into shares of Class A common stock (as a percent)	2400.00%	2400.00%
Common stock, stated value per share (in dollars per share)	$ 70	$ 70
Common stock, authorized (in shares)	2,544	2,546
Common stock, issued (in shares)	2,544	2,546
Common stock, outstanding (in shares)	2,544	2,546