Indemnity Shareholders' Equity and Noncontrolling Interest (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Reconciliation of the beginning and ending balances of Indemnity's shareholders' equity and the noncontrolling interest
Balance, beginning of period			$ 7,983	$ 7,550	$ 7,550
Net income	$ 33	$ 108	366	320	573
Change in accumulated other comprehensive income (loss), net of tax	(39)	$ (63)	(129)	74	0
Net purchase of treasury stock					(19)
Dividends declared:
Balance, end of period	8,125		8,125		7,983
Class A
Dividends declared:
Dividends declared			(94)		(120)
Class B
Dividends declared:
Dividends declared			(1)		(1)
Indemnity
Reconciliation of the beginning and ending balances of Indemnity's shareholders' equity and the noncontrolling interest
Balance, beginning of period			703	$ 734	734
Net income			145		168
Change in accumulated other comprehensive income (loss), net of tax			(3)		(59)
Net purchase of treasury stock					(19)
Dividends declared:
Balance, end of period	$ 750		$ 750		$ 703
Indemnity | Class A
Dividends declared:
Dividends declared (in dollars per share)	$ 0.6810	$ 0.6350	$ 2.0430	$ 1.9050	$ 2.5860
Dividends declared			$ (94)		$ (120)
Indemnity | Class B
Dividends declared:
Dividends declared (in dollars per share)	$ 102.1500	$ 95.2500	$ 306.4500	$ 285.7500	$ 387.9000
Dividends declared			$ (1)		$ (1)
Exchange
Reconciliation of the beginning and ending balances of Indemnity's shareholders' equity and the noncontrolling interest
Balance, beginning of period			7,280	$ 6,816	6,816
Net income			221		405
Change in accumulated other comprehensive income (loss), net of tax			(126)		59
Dividends declared:
Balance, end of period	$ 7,375		$ 7,375		$ 7,280