Derivative Financial Instruments - Derivatives Subject to a Master Netting Arrangement (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Liabilities
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	$ 325	$ 63
Derivatives in fair value hedge relationships
Assets
Gross Amount		2
Gross Amounts Netted in the Statements of Financial Condition		0
Net Amount Presented in the Statements of Financial Condition		2
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments		0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral		20
Liabilities
Gross Amount	0
Gross Amounts Netted in the Statements of Financial Condition	0
Net Amount Presented in the Statements of Financial Condition	0
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	2
Derivatives in fair value hedge relationships \| Interest rate swaps on AFS securities
Assets
Gross Amount		0
Gross Amounts Netted in the Statements of Financial Condition		0
Net Amount Presented in the Statements of Financial Condition		0
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments		0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral		6
Liabilities
Gross Amount	0
Gross Amounts Netted in the Statements of Financial Condition	0
Net Amount Presented in the Statements of Financial Condition	0
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	2
Derivatives in fair value hedge relationships \| Interest rate swaps on custodial deposits
Assets
Gross Amount		2
Gross Amounts Netted in the Statements of Financial Condition		0
Net Amount Presented in the Statements of Financial Condition		2
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments		0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral		14
Derivatives not designated as hedging instruments
Assets
Gross Amount	106	28
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	106	28
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	3	0
Liabilities
Gross Amount	288	17
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	288	17
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	300	63
Derivatives not designated as hedging instruments \| Mortgage-backed securities forwards
Assets
Gross Amount	39	2
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	39	2
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	0	0
Liabilities
Gross Amount	278	9
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	278	9
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	269	24
Derivatives not designated as hedging instruments \| Interest rate swaps and swaptions
Assets
Gross Amount	66	26
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	66	26
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	3	0
Derivatives not designated as hedging instruments \| Futures
Assets
Gross Amount	1
Gross Amounts Netted in the Statements of Financial Condition	0
Net Amount Presented in the Statements of Financial Condition	1
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	0
Derivatives not designated as hedging instruments \| Interest rate swaps and swamptions
Liabilities
Gross Amount	10	8
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	10	8
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	$ 31	$ 39

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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