Fair Value Measurements - Measured on a Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Assets
Mortgage loans held for sale	$ 3,179	$ 4,077
Forward mortgage servicing rights	2,757	3,496	$ 3,505
Derivative financial instruments	391	153
Liabilities
Mortgage servicing rights financing	49	37
Recurring Fair Value Measurements
Assets
Mortgage loans held for sale	3,179	4,077
Forward mortgage servicing rights	2,757	3,496
Derivative financial instruments	391	153
Total assets	6,327	7,727
Liabilities
Mortgage servicing rights financing	49	37
Excess spread financing	1,124	1,311
Total liabilities	1,223	1,363
Recurring Fair Value Measurements \| IRLCs
Assets
Derivative financial instruments	370	135
Recurring Fair Value Measurements \| Forward MBS trades
Assets
Derivative financial instruments	3	7
Liabilities
Derivative financial instruments	50	12
Recurring Fair Value Measurements \| LPCs
Assets
Derivative financial instruments	18	12
Liabilities
Derivative financial instruments	1	3
Recurring Fair Value Measurements \| Level 1
Assets
Mortgage loans held for sale	0	0
Forward mortgage servicing rights	0	0
Derivative financial instruments	0	0
Total assets	0	0
Liabilities
Mortgage servicing rights financing	0	0
Excess spread financing	0	0
Total liabilities	0	0
Recurring Fair Value Measurements \| Level 1 \| IRLCs
Assets
Derivative financial instruments	0	0
Recurring Fair Value Measurements \| Level 1 \| Forward MBS trades
Assets
Derivative financial instruments	0	0
Liabilities
Derivative financial instruments	0	0
Recurring Fair Value Measurements \| Level 1 \| LPCs
Assets
Derivative financial instruments	0	0
Liabilities
Derivative financial instruments		0
Recurring Fair Value Measurements \| Level 2
Assets
Mortgage loans held for sale	3,179	4,077
Forward mortgage servicing rights	0	0
Derivative financial instruments	3	153
Total assets	3,182	4,231
Liabilities
Mortgage servicing rights financing	0	0
Excess spread financing	0	0
Total liabilities	50	15
Recurring Fair Value Measurements \| Level 2 \| IRLCs
Assets
Derivative financial instruments	0	135
Recurring Fair Value Measurements \| Level 2 \| Forward MBS trades
Assets
Derivative financial instruments	3	7
Liabilities
Derivative financial instruments	50	12
Recurring Fair Value Measurements \| Level 2 \| LPCs
Assets
Derivative financial instruments	0	12
Liabilities
Derivative financial instruments		3
Recurring Fair Value Measurements \| Level 3
Assets
Mortgage loans held for sale	0	0
Forward mortgage servicing rights	2,757	3,496
Derivative financial instruments	388	0
Total assets	3,145	3,496
Liabilities
Mortgage servicing rights financing	49	37
Excess spread financing	1,124	1,311
Total liabilities	1,173	1,348
Recurring Fair Value Measurements \| Level 3 \| IRLCs
Assets
Derivative financial instruments	370	0
Recurring Fair Value Measurements \| Level 3 \| Forward MBS trades
Assets
Derivative financial instruments	0	0
Liabilities
Derivative financial instruments	0	0
Recurring Fair Value Measurements \| Level 3 \| LPCs
Assets
Derivative financial instruments	$ 18	0
Liabilities
Derivative financial instruments		$ 0

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Mortgage Servicing Rights Liability Resulting from Sale or Securitization of Servicer Advances, Rights not Accounted for as a Sale

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value, before effects of master netting arrangements, of a 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. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value of financial and nonfinancial obligations.

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Fair value portion of mortgage loans held-for-sale.

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- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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