Derivative Financial Instruments - Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Fair Value - Asset	$ 294.0		$ 153.0
Derivative Assets
Derivatives, Fair Value [Line Items]
Outstanding Notional	8,649.0	$ 3,190.0
Fair Value - Asset	294.0	72.0
Recorded Gains/(Losses)	141.0	9.0
Derivative Assets \| Loan sale commitments
Derivatives, Fair Value [Line Items]
Outstanding Notional	2,598.0	365.0
Fair Value - Asset	111.0	17.0
Recorded Gains/(Losses)	79.0	(9.0)
Derivative Assets \| IRLCs
Derivatives, Fair Value [Line Items]
Outstanding Notional	6,923.0	2,557.0
Fair Value - Asset	263.0	69.0
Recorded Gains/(Losses)	128.0	9.0
Derivative Assets \| Forward MBS trades
Derivatives, Fair Value [Line Items]
Outstanding Notional	886.0	410.0
Fair Value - Asset	6.0	1.0
Recorded Gains/(Losses)	0.0	(1.0)
Derivative Assets \| LPCs
Derivatives, Fair Value [Line Items]
Outstanding Notional	834.0	216.0
Fair Value - Asset	25.0	2.0
Recorded Gains/(Losses)	13.0	1.0
Derivative Assets \| Eurodollar futures
Derivatives, Fair Value [Line Items]
Outstanding Notional	6.0	7.0
Fair Value - Asset	0.0	0.0
Recorded Gains/(Losses)	0.0	0.0
Derivative Liabilities
Derivatives, Fair Value [Line Items]
Outstanding Notional	10,267.0	3,869.0
Fair Value - Liability	223.0	22.0
Recorded Gains/(Losses)	208.0	(3.0)
Derivative Liabilities \| IRLCs
Derivatives, Fair Value [Line Items]
Outstanding Notional	22.0
Fair Value - Liability	0.0
Recorded Gains/(Losses)	0.0
Derivative Liabilities \| Forward MBS trades
Derivatives, Fair Value [Line Items]
Outstanding Notional	10,229.0	3,804.0
Fair Value - Liability	223.0	22.0
Recorded Gains/(Losses)	211.0	(3.0)
Derivative Liabilities \| LPCs
Derivatives, Fair Value [Line Items]
Outstanding Notional	10.0	52.0
Fair Value - Liability	0.0	0.0
Recorded Gains/(Losses)	(3.0)	0.0
Derivative Liabilities \| Eurodollar futures
Derivatives, Fair Value [Line Items]
Outstanding Notional	6.0	13.0
Fair Value - Liability	0.0	0.0
Recorded Gains/(Losses)	$ 0.0	$ 0.0

Nominal or face amount used to calculate payments on the derivative asset.

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-Publisher FASB
-Name Accounting Standards Codification
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