- Quantitative Information - Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
FG VIEs' liabilities with recourse, at fair value [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Change in unrealized gains/(losses) related to financial instruments held	$ 1	$ (11)
Valuation, Income Approach [Member] | Credit derivative liabilities, net [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Inputs Hedge Cost	0.055%	0.176%
Fair Value Inputs Bank Profit	0.072%	0.06%
Fair Value Inputs Internal Floor	0.088%	0.08%
Valuation, Income Approach [Member] | Credit derivative liabilities, net [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Inputs Hedge Cost	0.825%	1.226%
Fair Value Inputs Bank Profit	5.099%	8.525%
Fair Value Inputs Internal Floor	0.30%	0.30%
Valuation, Income Approach [Member] | Credit derivative liabilities, net [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Inputs Hedge Cost	0.233%	0.481%
Fair Value Inputs Bank Profit	0.773%	1.075%
Fair Value Inputs Internal Floor	0.19%	0.218%
Level 3 [Member] | Valuation, Income Approach [Member] | Credit derivative liabilities, net [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total liabilities carried at fair value	$ (207)	$ (269)
Level 3 [Member] | Valuation, Income Approach [Member] | Credit derivative liabilities, net [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Year 1 loss estimates (as a percent)	0.00%	0.00%
Level 3 [Member] | Valuation, Income Approach [Member] | Credit derivative liabilities, net [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Year 1 loss estimates (as a percent)	66.00%	42.00%
Level 3 [Member] | Valuation, Income Approach [Member] | Credit derivative liabilities, net [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Year 1 loss estimates (as a percent)	2.20%	3.30%
Level 3 [Member] | Valuation, Income Approach [Member] | Financial Guarantee Variable Interest Entities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total liabilities carried at fair value	$ (619)	$ (757)
Level 3 [Member] | Valuation, Income Approach [Member] | Financial Guarantee Variable Interest Entities [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	5.00%	3.40%
Level 3 [Member] | Valuation, Income Approach [Member] | Financial Guarantee Variable Interest Entities [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	10.20%	10.00%
Level 3 [Member] | Valuation, Income Approach [Member] | Financial Guarantee Variable Interest Entities [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Yield (as a percent)	5.60%	4.90%