Fair Values (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Investment securities:
Equity securities	$ 1	$ 1
Debt securities and other	3,758	4,430
Derivative assets	544	991
Total assets	4,303	5,422
Level 1 [Member]
Investment securities:
Equity securities	1	1
Debt securities and other	409	350
Derivative assets	0	0
Total assets	410	351
Level 2 [Member]
Investment securities:
Equity securities	0	0
Debt securities and other	3,349	4,080
Derivative assets	545	991
Total assets	3,894	5,071
Level 3 [Member]
Investment securities:
Total assets	$ 0	$ 0