CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Cash and cash equivalents	$ 535	$ 400
Other assets	436	456
Indemnity
Fixed maturities, amortized cost	491	437
Equity securities, cost	48	54
Limited partnerships, cost	133	151
Cash and cash equivalents	33	12
Other assets	107	117
Treasury stock (in shares)	21,695,943	21,406,519
Exchange
Fixed maturities, amortized cost	7,541	7,016
Equity securities, cost	809	871
Trading securities, cost	2,157	1,910
Limited partnerships, cost	836	913
Cash and cash equivalents	502	388
Other assets	$ 329	$ 339
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	68,299,200
Common stock, outstanding (in shares)	46,603,257	46,892,681
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	2,542
Common stock, outstanding (in shares)	2,542	2,542