Fair Value of Financial Instruments - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value option elected aggregate carrying amount, asset	$ 333	$ 654
Residential loans
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value option elected aggregate carrying amount, asset	6,990	8,380
Business purpose residential loans, held-for-sale, at fair value
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value option elected aggregate carrying amount, asset	4,020	168
Multifamily loans
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value option elected aggregate carrying amount, asset	$ 1,430	2,130
Real estate securities | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Dealer marks of securities	83.00%
Percentage of carrying value for which dealer quotes were received on securities	94.00%
Percentage difference of internal valuation than dealer marks	1.00%
Servicer advance investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value option elected aggregate carrying amount, asset	$ 70	396
Excess MSRs
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value option elected aggregate carrying amount, asset	8	$ 25
Shared Home Appreciation Options
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value option elected aggregate carrying amount, asset	$ 43
MSRs | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Percentage difference of internal valuation than dealer marks	2.00%