Indemnity Earnings Per Share (Details) (Indemnity, USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2012	Mar. 31, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Class A
Reconciliation of the numerators and denominators used in the basic and diluted per-share computations
Class A common stock shares issued upon conversion of Class B common stock shares (in shares)		4,800
Income available to stockholders
Allocated net income (numerator) (in dollars)	$ 51		$ 47	$ 129	$ 142
Weighted shares (denominator) (in shares)	47,188,741		48,503,383	47,476,693	49,176,124
Per-share amount (in dollars per share)	$ 1.08		$ 0.97	$ 2.73	$ 2.90
Dilutive effect of stock-based awards
Allocated net income (numerator) (in dollars)	0		0	0	0
Weighted shares (denominator) (in shares)	80,505		71,238	80,505	71,238
Assumed conversion of Class B shares
Allocated net income (numerator) (in dollars)	0		0	1	1
Weighted shares (denominator) (in shares)	6,105,600		6,110,400	6,105,600	6,110,400
Income available to stockholders on equivalent shares
Allocated net income (numerator) (in dollars)	51		47	130	143
Weighted shares (denominator) (in shares)	53,374,846		54,685,021	53,662,798	55,357,762
Per-share amount (in dollars per share)	$ 0.96		$ 0.87	$ 2.43	$ 2.59
Class B
Reconciliation of the numerators and denominators used in the basic and diluted per-share computations
Ratio for converting shares of Class B common stock into shares of Class A common stock (as a percent)	2400.00%			2400.00%		2400.00%
Class B common stock shares converted into Class A common stock shares (in shares)		2
Income available to stockholders
Allocated net income (numerator) (in dollars)	0		0	1	1
Weighted shares (denominator) (in shares)	2,544		2,546	2,544	2,546
Per-share amount (in dollars per share)	$ 162.02		$ 146.67	$ 410.89	$ 439.39
Income available to stockholders on equivalent shares
Allocated net income (numerator) (in dollars)	$ 0		$ 0	$ 1	$ 1
Weighted shares (denominator) (in shares)	2,544		2,546	2,544	2,546
Per-share amount (in dollars per share)	$ 162.02		$ 146.67	$ 410.89	$ 439.39