Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net loss arising during the period, income tax expense (benefit)			$ (3)
Amortization of net loss included in net income, income tax expense (benefit)	2	1	7	4
Unrealized holding gain (loss) arising during the period, income tax expense (benefit)	(11)	(19)	(13)	(24)
Reclassification adjustments included in net income, income tax expense (benefit)	$ 1	$ 0	$ (12)	$ (12)