Earnings Per Share (Details) (Indemnity, USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 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)	$ 43		$ 52	$ 78	$ 95
Weighted shares (denominator) (in shares)	47,492,305		49,250,061	47,619,852	49,518,069
Per-share amount (in dollars per share)	$ 0.90		$ 1.05	$ 1.65	$ 1.93
Dilutive effect of stock-based awards
Allocated net income (numerator) (in dollars)	0		0	0	0
Weighted shares (denominator) (in shares)	79,943		76,515	79,943	76,515
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	6,108,000	6,110,400
Income available to stockholders on equivalent shares
Allocated net income (numerator) (in dollars)	43		52	79	96
Weighted shares (denominator) (in shares)	53,677,848		55,436,976	53,807,795	55,704,984
Per-share amount (in dollars per share)	$ 0.80		$ 0.94	$ 1.47	$ 1.72
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	2,545	2,546
Per-share amount (in dollars per share)	$ 134.78		$ 158.33	$ 248.55	$ 291.07
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	2,545	2,546
Per-share amount (in dollars per share)	$ 134.78		$ 158.33	$ 248.55	$ 291.07