CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Cash and cash equivalents	$ 365	$ 400
Other assets	451	456
Indemnity
Fixed maturities, amortized cost	430	437
Equity securities, cost	47	54
Limited partnerships, cost	138	151
Cash and cash equivalents	39	12
Other assets	115	117
Treasury stock (in shares)	21,622,913	21,406,519
Exchange
Fixed maturities, amortized cost	7,359	7,016
Equity securities, cost	915	871
Trading securities, cost	2,069	1,910
Limited partnerships, cost	880	913
Cash and cash equivalents	326	388
Other assets	$ 336	$ 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)	46,676,287	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