Indemnity Earnings Per Share (Details) (Indemnity, USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
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)									9,600
Income available to stockholders
Allocated net income (numerator) (in dollars)									$ 159	$ 168	$ 161
Weighted shares (denominator) (in shares)									47,357,836	48,875,316	50,705,607
Per-share amount (in dollars per share)	$ 0.63	$ 1.08	$ 0.90	$ 0.76	$ 0.55	$ 0.97	$ 1.05	$ 0.88	$ 3.38	$ 3.45	$ 3.18
Dilutive effect of stock-based awards
Allocated net income (numerator) (in dollars)									0	0	0
Weighted shares (denominator) (in shares)									84,397	71,721	68,887
Assumed conversion of Class B shares
Allocated net income (numerator) (in dollars)									1	1	1
Weighted shares (denominator) (in shares)									6,105,600	6,110,400	6,110,400
Income available to stockholders on equivalent shares
Allocated net income (numerator) (in dollars)									160	169	162
Weighted shares (denominator) (in shares)									53,547,833	55,057,437	56,884,894
Per-share amount (in dollars per share)	$ 0.56	$ 0.96	$ 0.80	$ 0.67	$ 0.49	$ 0.87	$ 0.94	$ 0.78	$ 2.99	$ 3.08	$ 2.85
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%	2400.00%
Class B common stock shares converted into Class A common stock shares (in shares)									4
Income available to stockholders
Allocated net income (numerator) (in dollars)									1	1	1
Weighted shares (denominator) (in shares)									2,544	2,546	2,546
Per-share amount (in dollars per share)	$ 94	$ 162.00	$ 135.00	$ 114.00	$ 82	$ 147.00	$ 158.00	$ 126.00	$ 505.00	$ 522.00	$ 463.00
Income available to stockholders on equivalent shares
Allocated net income (numerator) (in dollars)									$ 1	$ 1	$ 1
Weighted shares (denominator) (in shares)									2,544	2,546	2,546
Per-share amount (in dollars per share)	$ 94	$ 162.00	$ 135.00	$ 114.00	$ 82	$ 147.00	$ 158.00	$ 126.00	$ 505.00	$ 522.00	$ 463.00