Quarterly Results of Operations (unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Quarterly Results of Operations (unaudited)
Revenues	$ 1,418	$ 796	$ 1,245	$ 1,365	$ 1,401	$ 1,357	$ 916	$ 1,216	$ 4,824	$ 4,890	$ 4,255
Benefits and expenses	993	1,101	1,419	953	984	952	967	988	4,466	3,891	3,731
Income (loss) from operations before income taxes and noncontrolling interests	425	(305)	(174)	412	417	405	(51)	228	358	999	524
Net income (loss)	281	(180)	(107)	274	254	275	(31)	162	268	660	446
Less: Net income (loss) attributable to noncontrolling interest in consolidated entity - Exchange	255	(227)	(159)	230	242	221	(80)	115	99	498	338
Net income attributable to Indemnity	26	47	52	44	12	54	49	47	169	162	108
Indemnity
Quarterly Results of Operations (unaudited)
Income (loss) from operations before income taxes and noncontrolling interests									256	269	154
Net income (loss)									$ 169	$ 162	$ 108
Class A | Indemnity
Net income attributable to Indemnity per share
Common stock - basic (in dollars per share)	$ 0.55	$ 0.97	$ 1.05	$ 0.88	$ 0.25	$ 1.05	$ 0.96	$ 0.92	$ 3.45	$ 3.18	$ 2.10
Common stock - diluted (in dollars per share)	$ 0.49	$ 0.87	$ 0.94	$ 0.78	$ 0.22	$ 0.94	$ 0.86	$ 0.82	$ 3.08	$ 2.85	$ 1.89
Class B | Indemnity
Net income attributable to Indemnity per share
Common stock - basic (in dollars per share)	$ 81.76	$ 146.67	$ 158.33	$ 126.48	$ 40.93	$ 150.87	$ 138.21	$ 132.83	$ 522.47	$ 462.83	$ 312.45
Common stock - diluted (in dollars per share)	$ 81.76	$ 146.67	$ 158.33	$ 126.48	$ 40.93	$ 150.87	$ 138.21	$ 132.83	$ 522.47	$ 462.83	$ 312.45