Derivative Financial Instruments - Derivatives Subject to a Master Netting Arrangement (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Asset
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	$ 12
Liabilities
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	66	$ 114
Derivatives designated as hedging instruments
Asset
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 Instrument	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	1
Liabilities
Gross Amount	0	1
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	0	1
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instrument	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	14	14
Derivatives designated as hedging instruments | Interest rate swaps on AFS securities
Asset
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 Instrument	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	1
Liabilities
Gross Amount	0	0
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instrument	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	4	5
Derivatives designated as hedging instruments | Interest rate swaps on HFI residential first mortgages
Liabilities
Gross Amount	0	0
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instrument	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	1	1
Derivatives designated as hedging instruments | Interest rate swaps on custodial deposits
Liabilities
Gross Amount	0	1
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	0	1
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instrument	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	9	8
Derivatives not designated as hedging instruments
Asset
Gross Amount	87	73
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	87	73
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instrument	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	29	6
Liabilities
Gross Amount	20	102
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	20	102
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instrument	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	33	94
Derivatives not designated as hedging instruments | Mortgage-backed securities forwards
Asset
Gross Amount	10	14
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	10	14
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instrument	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	12	0
Liabilities
Gross Amount	14	98
Gross Amounts Netted in the Statements of Financial Condition	0	0
Net Amount Presented in the Statements of Financial Condition	14	98
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instrument	0	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	9	68
Derivatives not designated as hedging instruments | Interest rate swaptions
Asset
Gross Amount	77
Gross Amounts Netted in the Statements of Financial Condition	0
Net Amount Presented in the Statements of Financial Condition	77
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instrument	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	17
Derivatives not designated as hedging instruments | Interest rate swaps
Asset
Gross Amount		59
Gross Amounts Netted in the Statements of Financial Condition		0
Net Amount Presented in the Statements of Financial Condition		59
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instrument		0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral		6
Liabilities
Gross Amount	6
Gross Amounts Netted in the Statements of Financial Condition	0
Net Amount Presented in the Statements of Financial Condition	6
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instrument	0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral	$ 24
Derivatives not designated as hedging instruments | Interest rate swaps and swaptions
Liabilities
Gross Amount		4
Gross Amounts Netted in the Statements of Financial Condition		0
Net Amount Presented in the Statements of Financial Condition		4
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instrument		0
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral		$ 26