Rollforward of Mortgage Servicing Rights, at Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Servicing Asset at Fair Value, Amount [Roll Forward]
Mortgage servicing rights, at fair value, at beginning of period	$ 1,505,163	$ 2,014,370	$ 1,909,444	$ 1,993,440
Purchases of mortgage servicing rights	21,551	43,710	205,334	264,522
Sales of mortgage servicing rights	381	0	1,814	0
Changes in valuation inputs or assumptions used in the valuation model	(111,013)	(182,025)	(611,776)	(333,639)
Other changes in fair value	(127,778)	(70,407)	(213,680)	(108,056)
Other changes	(9,109)	(4,822)	(11,941)	(15,441)
Mortgage servicing rights, at fair value, at end of period	1,279,195	$ 1,800,826	1,279,195	$ 1,800,826
Mortgage servicing rights, at fair value, pledged as collateral for borrowings	$ 1,200,000		$ 1,200,000		$ 1,600,000