Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Nonrecurring Basis (Details) - Nonrecurring [Member] - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
ASSETS MEASURED ON A NONRECURRING BASIS
Impaired loans and leases	$ 57	$ 42
Accrued income and other assets	21	16
Total assets at fair value	78	58
Level 1 [Member]
ASSETS MEASURED ON A NONRECURRING BASIS
Impaired loans and leases	0	0
Accrued income and other assets	0	0
Total assets at fair value	0	0
Level 2 [Member]
ASSETS MEASURED ON A NONRECURRING BASIS
Impaired loans and leases	0	0
Accrued income and other assets	0	0
Total assets at fair value	0	0
Level 3 [Member]
ASSETS MEASURED ON A NONRECURRING BASIS
Impaired loans and leases	57	42
Accrued income and other assets	21	16
Total assets at fair value	$ 78	$ 58