Income Taxes Income Taxes - Effective Tax Rates Differing From Prevailing Federal Corporate Income Tax Rates (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Effective Tax Rates [Line Items]
Tax on income from continuing operations at statutory rate									$ (92)	$ (38)	$ 57
Tax on income from continuing operations at statutory rate,tax rate									21.00%	21.00%	21.00%
Tax-exempt interest									$ (2)	$ (3)	$ (7)
Tax-exempt interest, tax rate									0.40%	1.80%	(2.50%)
Derivative, Gain (Loss) on Derivative, Net	$ 12	$ 7	$ 2	$ (70)	$ 12	$ (10)	$ (35)	$ (16)	$ (50)	$ (50)	$ 7
Valuation allowance									$ 113	$ 8	$ 5
Valuation allowance, tax rate									(25.60%)	(4.40%)	1.90%
Foreign taxes									$ 6	$ 40	$ 10
Foreign taxes, tax rate									(1.40%)	(22.10%)	3.90%
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount									$ (29)	$ 28	$ (60)
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Percent									6.70%	(15.30%)	(22.00%)
Other, net									$ 0	$ (2)	$ 1
Other, net, tax rate									0.00%	1.30%	0.40%
Income tax expense (benefit)									$ (3)	$ 32	$ 5
Effective Income Tax Rate Reconciliation, Percent									0.70%	(17.70%)	2.00%
Income Tax Reconciliation Tax Bankruptcy Adjustments									$ 0	$ 0	$ (2)
Effective income Tax Reconciliation Tax Bankruptcy Adjustments									0.00%	0.00%	(0.70%)
Variable Interest Entity, Primary Beneficiary [Member] | Income Loss On Variable Interest Entities [Member]
Reconciliation of Effective Tax Rates [Line Items]
Derivative, Gain (Loss) on Derivative, Net									$ (144)	$ (32)	$ 505
Variable Interest Entity, Primary Beneficiary [Member] | Currency Swaps [Member] | Income Loss On Variable Interest Entities [Member]
Reconciliation of Effective Tax Rates [Line Items]
Derivative, Gain (Loss) on Derivative, Net									(6)	(12)	11
Variable Interest Entity, Primary Beneficiary [Member] | Interest Rate Swaps [Member] | Income Loss On Variable Interest Entities [Member]
Reconciliation of Effective Tax Rates [Line Items]
Derivative, Gain (Loss) on Derivative, Net									$ (138)	$ (20)	$ 493