Indemnity Earnings Per Share (Details) (Indemnity, USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
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)	$ 36	$ 36
Weighted shares (denominator) (in shares)	46,774,968	47,749,799
Per-share amount (in dollars per share)	$ 0.78	$ 0.76
Dilutive effect of stock-based awards
Allocated net income (numerator) (in dollars)	0	0
Weighted shares (denominator) (in shares)	84,397	72,245
Assumed conversion of Class B shares
Allocated net income (numerator) (in dollars)	1	0
Weighted shares (denominator) (in shares)	6,100,800	6,108,000
Income available to stockholders on equivalent shares
Allocated net income (numerator) (in dollars)	37	36
Weighted shares (denominator) (in shares)	52,960,165	53,930,044
Per-share amount (in dollars per share)	$ 0.69	$ 0.67
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%
Class B common stock shares converted into Class A common stock shares (in shares)	0	2
Income available to stockholders
Allocated net income (numerator) (in dollars)	0	0
Weighted shares (denominator) (in shares)	2,542	2,545
Per-share amount (in dollars per share)	$ 117.00	$ 114.00
Income available to stockholders on equivalent shares
Allocated net income (numerator) (in dollars)	$ 0	$ 0
Weighted shares (denominator) (in shares)	2,542	2,545
Per-share amount (in dollars per share)	$ 117.00	$ 114.00