Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Nonrecurring Basis (Details) - Fair Value, Nonrecurring [Member] - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
ASSETS MEASURED ON A NONRECURRING BASIS
Impaired loans and leases	$ 76	$ 42
Accrued income and other assets	169	16
Total assets on a recurring basis at fair value	245	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 on a recurring basis 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	118	0
Total assets on a recurring basis at fair value	118	0
Level 3 [Member]
ASSETS MEASURED ON A NONRECURRING BASIS
Impaired loans and leases	76	42
Accrued income and other assets	51	16
Total assets on a recurring basis at fair value	$ 127	$ 58