Repurchase Agreements And Other Debt (Repurchase Arrangements And Weighted Average Interest Rates Classified By Original Maturities) (Details) $ in Millions	Sep. 30, 2016 USD ($) days	Dec. 31, 2015 USD ($) days
Repurchase Agreements | $	$ 37,668	$ 41,754
Weighted Average Days to Maturity | days	198	173
30 Days or Less [Member]
Repurchase Agreements | $	$ 17,198	$ 17,579
Weighted Average Interest Rate	0.72%	0.54%
Weighted Average Days to Maturity | days	11	14
1 to 3 Months
Repurchase Agreements | $	$ 9,318	$ 14,283
Weighted Average Interest Rate	0.79%	0.64%
Weighted Average Days to Maturity | days	50	58
3 to 6 Months
Repurchase Agreements | $	$ 3,617	$ 3,154
Weighted Average Interest Rate	0.90%	0.61%
Weighted Average Days to Maturity | days	126	121
6 to 9 Months
Repurchase Agreements | $	$ 765	$ 589
Weighted Average Interest Rate	0.85%	0.65%
Weighted Average Days to Maturity | days	221	199
9 to 12 Months
Repurchase Agreements | $	$ 615	$ 1,201
Weighted Average Interest Rate	0.95%	0.65%
Weighted Average Days to Maturity | days	309	307
12 to 24 Months
Repurchase Agreements | $	$ 1,985	$ 1,473
Weighted Average Interest Rate	1.09%	0.73%
Weighted Average Days to Maturity | days	495	600
24 to 36 Months
Repurchase Agreements | $	$ 1,100	$ 650
Weighted Average Interest Rate	1.21%	0.81%
Weighted Average Days to Maturity | days	926	901
36 to 48 months
Repurchase Agreements | $	$ 2,100	$ 1,300
Weighted Average Interest Rate	1.15%	0.86%
Weighted Average Days to Maturity | days	1,216	1,231
48 to 60 Months
Repurchase Agreements | $	$ 925	$ 1,500
Weighted Average Interest Rate	1.23%	0.76%
Weighted Average Days to Maturity | days	1,559	1,477
Maturity Overnight [Member]
Weighted Average Interest Rate	0.85%	0.00%
Weighted Average Days to Maturity | days	3	1
Repurchase Agreements [Member]
Weighted Average Interest Rate	0.83%	0.61%
Agency Securities [Member]
Repurchase Agreements | $	$ 37,623	$ 41,729
Weighted Average Days to Maturity | days	199	173
Agency Securities [Member] | Repurchase Agreements [Member]
Weighted Average Interest Rate	0.83%	0.61%
US Treasury Securities [Member]
Repurchase Agreements | $	$ 45	$ 25