CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Cash and cash equivalents	$ 400	$ 185
Other assets	456	441
Indemnity
Fixed maturities, amortized cost	437	535
Equity securities, cost	54	24
Trading securities, cost	0	23
Limited partnerships, cost	151	185
Cash and cash equivalents	12	11
Other assets	117	119
Treasury stock (in shares)	21,406,519	20,427,758
Exchange
Fixed maturities, amortized cost	7,016	6,829
Equity securities, cost	871	531
Trading securities, cost	1,910	2,021
Limited partnerships, cost	913	1,003
Cash and cash equivalents	388	174
Other assets	$ 339	$ 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)	68,299,200	68,289,600
Common stock, outstanding (in shares)	46,892,681	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)	3,070	3,070
Common stock, issued (in shares)	2,542	2,546
Common stock, outstanding (in shares)	2,542	2,546