Quarterly Results of Operations (unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Results of Operations (unaudited)
Revenues	$ 1,589	$ 1,426	$ 1,598	$ 1,511	$ 1,697	$ 1,577	$ 1,426	$ 1,571	$ 6,124	$ 6,271	$ 5,512
Benefits and expenses	1,212	1,276	1,451	1,355	1,227	1,179	1,163	1,135	5,294	4,704	4,613
Income (loss) from operations before income taxes and noncontrolling interest	377	150	147	156	470	398	263	436	830	1,567	899
Net income (loss)	253	108	103	109	314	267	177	290	573	1,048	619
Less: Net income (loss) attributable to noncontrolling interest in consolidated entity – Exchange	227	61	54	63	278	221	133	253	405	885	459
Net income (loss) attributable to Indemnity	26	47	49	46	36	46	44	37	168	163	160
Indemnity
Quarterly Results of Operations (unaudited)
Income (loss) from operations before income taxes and noncontrolling interest									251	247	241
Net income (loss) attributable to Indemnity									$ 168	$ 163	$ 160
Class A | Indemnity
Net income attributable to Indemnity per share
Common stock - basic (in dollars per share)	$ 0.54	$ 1.01	$ 1.05	$ 0.99	$ 0.75	$ 0.98	$ 0.95	$ 0.78	$ 3.59	$ 3.46	$ 3.38
Common stock - diluted (in dollars per share)	$ 0.48	$ 0.90	$ 0.94	$ 0.88	$ 0.67	$ 0.87	$ 0.84	$ 0.69	$ 3.18	$ 3.08	$ 2.99
Class B | Indemnity
Net income attributable to Indemnity per share
Common stock - basic (in dollars per share)	$ 81	$ 151.00	$ 158.00	$ 149.00	$ 113.00	$ 147.00	$ 142.00	$ 117.00	$ 539.00	$ 520.00	$ 505.00
Common stock - diluted (in dollars per share)	$ 81	$ 151.00	$ 158.00	$ 149.00	$ 113.00	$ 147.00	$ 142.00	$ 117.00	$ 538.00	$ 519.00	$ 505.00