Quarterly Results of Operations (unaudited) (Details) (USD $) In Millions, except Per 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
Quarterly Results of Operations (unaudited)
Revenues	$ 1,372	$ 1,460	$ 1,160	$ 1,520	$ 1,418	$ 796	$ 1,245	$ 1,365	$ 5,512	$ 4,824	$ 4,890
Benefits and expenses	1,207	1,190	1,230	986	993	1,101	1,419	953	4,613	4,466	3,891
Income (loss) from operations before income taxes and noncontrolling interest	165	270	(70)	534	425	(305)	(174)	412	899	358	999
Net income (loss)	119	184	(38)	354	281	(180)	(107)	274	619	268	660
Less: Net income attributable to noncontrolling interest in consolidated entity – Exchange	89	133	(81)	318	255	(227)	(159)	230	459	99	498
Net income attributable to Indemnity	30	51	43	36	26	47	52	44	160	169	162
Indemnity
Quarterly Results of Operations (unaudited)
Income (loss) from operations before income taxes and noncontrolling interest									241	256	269
Net income attributable to Indemnity									$ 160	$ 169	$ 162
Class A | Indemnity
Earnings Per Share [Abstract]
Common stock - basic (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
Common stock - diluted (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 | Indemnity
Earnings Per Share [Abstract]
Common stock - basic (in dollars per share)	$ 94	$ 162.00	$ 135.00	$ 114.00	$ 82	$ 147.00	$ 158.00	$ 126.00	$ 505.00	$ 522.00	$ 463.00
Common stock - diluted (in dollars per share)	$ 94	$ 162.00	$ 135.00	$ 114.00	$ 82	$ 147.00	$ 158.00	$ 126.00	$ 505.00	$ 522.00	$ 463.00