Mortgage Servicing - Summary of Geographic Distributions of UPB and Count of Residential Loans and Real Estate Serviced (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) loan	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Amount	$ 212,366,431	$ 256,000,490	$ 179,352,553
Residential Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Amount	$ 212,366,431
Count | loan	1,419,943
California | Residential Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Amount	$ 47,350,699
Count | loan	189,959
New York | Residential Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Amount	$ 19,557,621
Count | loan	90,805
Florida | Residential Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Amount	$ 16,366,372
Count | loan	121,875
New Jersey | Residential Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Amount	$ 10,921,867
Count | loan	57,182
Texas | Residential Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Amount	$ 10,073,637
Count | loan	100,868
Other | Residential Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Amount	$ 108,096,235
Count | loan	859,254