Investment Securities - Cost/Amortized, Unrealized Gains/Losses & FV on AFS Investment Securities (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Cost/ Amortized Cost	$ 1,705,000,000	$ 1,745,000,000
Unrealized Gains	107,000,000	55,000,000
Unrealized Losses	(6,000,000)	(2,000,000)
Fair Value	1,806,000,000	1,798,000,000
Allowance for credit loss	0
U.S. government and government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Cost/ Amortized Cost	12,000,000	11,000,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	12,000,000	11,000,000
Obligations of states, municipalities, and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Cost/ Amortized Cost	81,000,000	91,000,000
Unrealized Gains	5,000,000	2,000,000
Unrealized Losses	0	(1,000,000)
Fair Value	86,000,000	92,000,000
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Cost/ Amortized Cost	24,000,000	91,000,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	24,000,000	91,000,000
Non-U.S. government and government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Cost/ Amortized Cost	132,000,000	144,000,000
Unrealized Gains	9,000,000	3,000,000
Unrealized Losses	0
Fair Value	141,000,000	147,000,000
Corporate debt
Debt Securities, Available-for-sale [Line Items]
Cost/ Amortized Cost	1,106,000,000	1,054,000,000
Unrealized Gains	83,000,000	45,000,000
Unrealized Losses	(5,000,000)	(1,000,000)
Fair Value	1,184,000,000	1,098,000,000
RMBS
Debt Securities, Available-for-sale [Line Items]
Cost/ Amortized Cost	211,000,000	214,000,000
Unrealized Gains	7,000,000	3,000,000
Unrealized Losses	0	0
Fair Value	218,000,000	217,000,000
CMBS
Debt Securities, Available-for-sale [Line Items]
Cost/ Amortized Cost	61,000,000	56,000,000
Unrealized Gains	2,000,000	1,000,000
Unrealized Losses	0
Fair Value	63,000,000	57,000,000
CDO/ABS
Debt Securities, Available-for-sale [Line Items]
Cost/ Amortized Cost	78,000,000	84,000,000
Unrealized Gains	1,000,000	1,000,000
Unrealized Losses	(1,000,000)	0
Fair Value	$ 78,000,000	$ 85,000,000