Derivative Financial Instruments - Derivatives Subject to a Master Netting Arrangement (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Assets
Gross amounts not offset in the statement of financial position, cash collateral		$ 14
Liabilities
Gross amounts not offset in the statement of financial position, cash collateral	$ 63	53
Designated as hedging instrument
Liabilities
Gross amounts not offset in the statement of financial position, cash collateral	29	23
Not designated as hedging instrument
Assets
Gross Amount	28	27
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amount Presented in the Statement of Financial Position	28	27
Gross amounts not offset in the statement of financial position, financial instrument	0	0
Gross amounts not offset in the statement of financial position, cash collateral	0	14
Liabilities
Gross Amount	17	39
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amount Presented in the Statement of Financial Position	17	39
Gross amounts not offset in the statement of financial position, financial instrument	0	0
Gross amounts not offset in the statement of financial position, cash collateral	63	53
Not designated as hedging instrument \| Mortgage-backed securities forwards
Assets
Gross Amount	2	4
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amount Presented in the Statement of Financial Position	2	4
Gross amounts not offset in the statement of financial position, financial instrument	0	0
Gross amounts not offset in the statement of financial position, cash collateral	0	0
Liabilities
Gross Amount	9	31
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amount Presented in the Statement of Financial Position	9	31
Gross amounts not offset in the statement of financial position, financial instrument	0	0
Gross amounts not offset in the statement of financial position, cash collateral	24	29
Not designated as hedging instrument \| Interest rate swaps and swaptions
Assets
Gross Amount	26	23
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amount Presented in the Statement of Financial Position	26	23
Gross amounts not offset in the statement of financial position, financial instrument	0	0
Gross amounts not offset in the statement of financial position, cash collateral	0	14
Not designated as hedging instrument \| Futures
Liabilities
Gross Amount		1
Gross Amounts Offset in the Statement of Financial Position		0
Net Amount Presented in the Statement of Financial Position		1
Gross amounts not offset in the statement of financial position, financial instrument		0
Gross amounts not offset in the statement of financial position, cash collateral		1
Not designated as hedging instrument \| Interest rate swaps and swaptions
Liabilities
Gross Amount	8	7
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amount Presented in the Statement of Financial Position	8	7
Gross amounts not offset in the statement of financial position, financial instrument	0	0
Gross amounts not offset in the statement of financial position, cash collateral	$ 39	$ 23

Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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