Fair Value - Level 3 Input Roll Forward, Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Mortgage servicing liabilities resulting from loan sales	$ 6,576	$ 794
Excess servicing spread financing
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	178,586	216,110
Accrual of interest on excess servicing spread financing	1,974	3,066
Repayment	(9,308)	(10,552)
Changes in fair value included in income	(14,522)	(4,051)
Balance at the end of the period	157,109	205,081
Recurring basis
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	3,455,505	3,156,728
Purchases and issuances, net	2,008,971	1,078,872
Capitalization of interest and advances	18,027
Sales and repayments	(738,928)	(187,738)
Mortgage servicing rights resulting from loan sales	282,315	115,751
Changes in fair value included in income arising from:
Changes in instrument specific credit risk	(7,523)	(6,091)
Other factors	(841,250)	(199,624)
Total changes in fair value included in income	(848,773)	(205,715)
Transfers from mortgage loans held for sale from Level 3 to Level 2	(489,407)	(405,163)
Transfers to real estate acquired in settlement of loans	(691)	(1,181)
Transfers from interest rate lock commitments to loans held for sale	(363,354)	(100,234)
Balance at the end of the period	3,323,665	3,451,320
Changes in fair value recognized during the period relating to assets still held at the end of the period	(737,830)	(196,520)
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	207,726	224,791
Issuances	379	508
Accrual of interest on excess servicing spread financing	1,974	3,066
Repayment	(9,308)	(10,552)
Mortgage servicing liabilities resulting from loan sales	6,576	794
Changes in fair value included in income	(20,477)	(5,682)
Balance at the end of the period	186,870	212,925
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	(20,477)	(5,682)
Recurring basis | Excess servicing spread financing
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	178,586	216,110
Issuances	379	508
Accrual of interest on excess servicing spread financing	1,974	3,066
Repayment	(9,308)	(10,552)
Changes in fair value included in income	(14,522)	(4,051)
Balance at the end of the period	157,109	205,081
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	(14,522)	(4,051)
Recurring basis | Mortgage servicing liabilities
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	29,140	8,681
Mortgage servicing liabilities resulting from loan sales	6,576	794
Changes in fair value included in income	(5,955)	(1,631)
Balance at the end of the period	29,761	7,844
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	(5,955)	(1,631)
Recurring basis | Loans held for sale
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	383,878	260,008
Purchases and issuances, net	1,641,231	784,262
Capitalization of interest and advances	18,027
Sales and repayments	(738,928)	(176,302)
Changes in fair value included in income arising from:
Changes in instrument specific credit risk	(7,523)	(6,091)
Total changes in fair value included in income	(7,523)	(6,091)
Transfers from mortgage loans held for sale from Level 3 to Level 2	(489,407)	(405,163)
Transfers to real estate acquired in settlement of loans	(691)	(1,181)
Balance at the end of the period	806,587	455,533
Changes in fair value recognized during the period relating to assets still held at the end of the period	(11,856)	(3,540)
Recurring basis | Interest rate lock commitments
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	136,650	49,338
Purchases and issuances, net	341,980	56,983
Changes in fair value included in income arising from:
Other factors	199,918	59,978
Total changes in fair value included in income	199,918	59,978
Transfers from interest rate lock commitments to loans held for sale	(363,354)	(100,234)
Balance at the end of the period	315,194	66,065
Changes in fair value recognized during the period relating to assets still held at the end of the period	315,194	66,065
Recurring basis | Repurchase agreement derivatives
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	8,187	26,770
Purchases and issuances, net		9,855
Sales and repayments		(11,436)
Changes in fair value included in income arising from:
Other factors		(557)
Total changes in fair value included in income		(557)
Balance at the end of the period	8,187	24,632
Recurring basis | Mortgage servicing rights
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	2,926,790	2,820,612
Purchases and issuances, net	25,760	227,772
Mortgage servicing rights resulting from loan sales	282,315	115,751
Changes in fair value included in income arising from:
Other factors	(1,041,168)	(259,045)
Total changes in fair value included in income	(1,041,168)	(259,045)
Balance at the end of the period	2,193,697	2,905,090
Changes in fair value recognized during the period relating to assets still held at the end of the period	$ (1,041,168)	$ (259,045)