Earnings Per Share (Details) (Indemnity, USD $) In Millions, except Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Indemnity Earnings Per Share Calculation
Class B shares are convertible into Class A shares at a conversion ratio of 2,400 to 1 (in shares)	2,400		2,400
Class B shares are convertible into Class A shares at a conversion ratio of 2,400 to 1 (in shares)	1		1
Class A
Income available to stockholders
Allocated net income (numerator) (in dollars)	$ 52	$ 49	$ 95	$ 95
Weighted shares (denominator) (in shares)	49,250,061	51,013,358	49,518,069	51,099,071
Per-share amount (in dollars per share)	$ 1.05	$ 0.96	$ 1.93	$ 1.87
Dilutive effect of stock awards
Allocated net income (numerator) (in dollars)	0	0	0	0
Weighted shares (denominator) (in shares)	76,515	73,845	76,515	73,213
Assumed conversion of Class B shares
Allocated net income (numerator) (in dollars)	0	0	1	1
Weighted shares (denominator) (in shares)	6,110,400	6,110,400	6,110,400	6,110,400
Income available to stockholders on equivalent shares
Allocated net income (numerator) (in dollars)	52	49	96	96
Weighted shares (denominator) (in shares)	55,436,976	57,197,603	55,704,984	57,282,684
Per-share amount (in dollars per share)	$ 0.94	$ 0.86	$ 1.72	$ 1.68
Class A | Other stock-based awards
Income available to stockholders on equivalent shares
Dilutive effect of stock awards not yet vested (in shares)	6,400	11,200	6,400	11,200
Class A | Stock compensation plan for outside directors
Income available to stockholders on equivalent shares
Dilutive effect of stock awards not yet vested (in shares)	6,682	10,612	6,682	10,612
Dilutive effect of vested stock awards (in shares)	63,433	50,748	63,433	50,748
Class B
Indemnity Earnings Per Share Calculation
Class B shares are convertible into Class A shares at a conversion ratio of 2,400 to 1 (in shares)	2,400		2,400		2,400
Class B shares are convertible into Class A shares at a conversion ratio of 2,400 to 1 (in shares)	1		1		1
Income available to stockholders
Allocated net income (numerator) (in dollars)	0	0	1	1
Weighted shares (denominator) (in shares)	2,546	2,546	2,546	2,546
Per-share amount (in dollars per share)	$ 158.33	$ 138.21	$ 291.07	$ 271.03
Income available to stockholders on equivalent shares
Allocated net income (numerator) (in dollars)	$ 0	$ 0	$ 1	$ 1
Weighted shares (denominator) (in shares)	2,546	2,546	2,546	2,546
Per-share amount (in dollars per share)	$ 158.33	$ 138.21	$ 291.07	$ 271.03