Indemnity Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive (loss) income	$ 0	$ (144)	$ 150
Indemnity
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	(59)	(133)
Other comprehensive (loss) income before reclassifications, net of tax	(63)	65
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	4	9
Other comprehensive (loss) income	(59)	74
Balance, end of year	(118)	(59)
Indemnity | Unrealized holding gains (losses) on available-for-sale securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	6	13
Other comprehensive (loss) income before reclassifications, net of tax	2	(6)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	(1)	(1)
Other comprehensive (loss) income	1	(7)
Balance, end of year	7	6
Indemnity | Postretirement Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	(65)	(146)
Other comprehensive (loss) income before reclassifications, net of tax	(65)	71
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	5	10
Other comprehensive (loss) income	(60)	81
Balance, end of year	$ (125)	$ (65)