Indemnity Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Changes in Indemnity's accumulated other comprehensive income (loss) by component attributable to the Indemnity shareholder interest
Other comprehensive (loss) income	$ (22)	$ 72	$ 150
Indemnity
Changes in Indemnity's accumulated other comprehensive income (loss) by component attributable to the Indemnity shareholder interest
Balance, beginning of period	(133)
Other comprehensive loss before reclassifications, net of tax	(1)
Amounts reclassified from accumulated other comprehensive loss, net of tax(1)	0
Other comprehensive (loss) income	(1)		(28)
Balance, end of period	(134)		(133)
Indemnity | Unrealized holding gains (losses) on available-for-sale securities
Changes in Indemnity's accumulated other comprehensive income (loss) by component attributable to the Indemnity shareholder interest
Balance, beginning of period	13
Other comprehensive loss before reclassifications, net of tax	(1)
Amounts reclassified from accumulated other comprehensive loss, net of tax(1)	0
Other comprehensive (loss) income	(1)
Balance, end of period	12
Indemnity | Postretirement Plans
Changes in Indemnity's accumulated other comprehensive income (loss) by component attributable to the Indemnity shareholder interest
Balance, beginning of period	(146)
Other comprehensive loss before reclassifications, net of tax	0
Amounts reclassified from accumulated other comprehensive loss, net of tax(1)	0
Other comprehensive (loss) income	0
Balance, end of period	$ (146)