Recent Accounting Pronouncements (Details) (USD $)	1 Months Ended	9 Months Ended
	Jan. 31, 2010	Sep. 30, 2010	Sep. 30, 2011
Recent Accounting Pronouncements
Cumulative effect increase in assets	$ 5,500,000,000
Cumulative effect increase in liabilities	5,100,000,000
Cumulative effect increase in appropriated retained earnings	473,000,000	473,000,000
Expected reduction to retained earnings range lower end			1,300,000,000
Expected reduction to retained earnings range upper end			$ 1,400,000,000