Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Net gain arising during the period, income tax expense	$ 0	$ 0	$ 0	$ 2
Amortization of net (gain) loss included in net income, income tax expense (benefit)	1	1	4	(3)
Prior service credit arising during the period, income tax expense	0	0	0	1
Amortization of prior service credit, income tax benefit	0	0	0	(1)
Unrealized holding gain (loss) arising during the period, income tax expense (benefit)	(19)	29	(24)	41
Reclassification adjustments included in net income, income tax benefit	$ 0	$ 5	$ 12	$ 54