Fair Values (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Investment securities:
Equity securities and other	$ 49	$ 50
Debt securities	3,679	3,709
Derivatives	720	544
Total assets	4,448	4,303
Level 1 [Member]
Investment securities:
Equity securities and other	1	1
Debt securities	541	409
Derivatives	0	0
Total assets	542	410
Level 2 [Member]
Investment securities:
Equity securities and other	48	49
Debt securities	3,138	3,300
Derivatives	720	544
Total assets	3,906	3,893
Level 3 [Member]
Investment securities:
Equity securities and other	0	0
Debt securities	0	0
Derivatives	0	0
Total assets	$ 0	$ 0