Fair Value - Level 3 Input Roll Forward, Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Mortgage servicing liabilities resulting from loan sales			$ 6,576	$ 7,632
Recurring basis
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	$ 3,323,665	$ 3,451,320	3,455,505	3,156,728
Purchases and issuances, net	785,005	1,014,315	2,793,976	2,093,187
Capitalization of interest and advances	14,994		33,021
Sales and repayments	(60,364)	(667,169)	(799,292)	(854,907)
Mortgage servicing rights resulting from loan sales	225,534	183,331	507,849	299,082
Changes in fair value included in income arising from:
Changes in instrument specific credit risk	1,132	(186)	(6,391)	(6,277)
Other factors	91,506	(272,083)	(749,744)	(471,707)
Total changes in fair value included in income	92,638	(272,269)	(756,135)	(477,984)
Transfers from mortgage loans held for sale from Level 3 to Level 2	(389,486)	(471,599)	(878,893)	(876,762)
Transfers to real estate acquired in settlement of loans		(863)	(691)	(2,044)
Transfers from interest rate lock commitments to loans held for sale	(740,477)	(170,942)	(1,103,831)	(271,176)
Balance at the end of the period	3,251,509	3,066,124	3,251,509	3,066,124
Changes in fair value recognized during the period relating to assets still held at the end of the period	161,655	(259,604)	(879,359)	(519,118)
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	186,870	212,925	207,726	224,791
Issuances	483	442	862	950
Accrual of interest on excess servicing spread financing	2,372	2,767	4,346	5,833
Repayment	(8,122)	(10,530)	(17,430)	(21,082)
Mortgage servicing liabilities resulting from loan sales		6,838	6,576	7,632
Changes in fair value included in income	(539)	(5,338)	(21,016)	(11,020)
Balance at the end of the period	181,064	207,104	181,064	207,104
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	(539)	(5,338)	(21,016)	(11,020)
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	157,109	205,081	178,586	216,110
Issuances	483	442	862	950
Accrual of interest on excess servicing spread financing	2,372	2,767	4,346	5,833
Repayment	(8,122)	(10,530)	(17,430)	(21,082)
Changes in fair value included in income	(636)	(3,604)	(15,158)	(7,655)
Balance at the end of the period	151,206	194,156	151,206	194,156
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	(636)	(3,604)	(15,158)	(7,655)
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	29,761	7,844	29,140	8,681
Mortgage servicing liabilities resulting from loan sales		6,838	6,576	7,632
Changes in fair value included in income	97	(1,734)	(5,858)	(3,365)
Balance at the end of the period	29,858	12,948	29,858	12,948
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	97	(1,734)	(5,858)	(3,365)
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	806,587	455,533	383,878	260,008
Purchases and issuances, net	288,856	891,146	1,930,087	1,675,408
Capitalization of interest and advances	14,994		33,021
Sales and repayments	(60,364)	(656,033)	(799,292)	(832,335)
Changes in fair value included in income arising from:
Changes in instrument specific credit risk	1,132	(186)	(6,391)	(6,277)
Total changes in fair value included in income	1,132	(186)	(6,391)	(6,277)
Transfers from mortgage loans held for sale from Level 3 to Level 2	(389,486)	(471,599)	(878,893)	(876,762)
Transfers to real estate acquired in settlement of loans		(863)	(691)	(2,044)
Balance at the end of the period	661,719	217,998	661,719	217,998
Changes in fair value recognized during the period relating to assets still held at the end of the period	(717)	(3,911)	(563)	(4,380)
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	315,194	66,065	136,650	49,338
Purchases and issuances, net	496,149	119,880	838,129	176,863
Changes in fair value included in income arising from:
Other factors	297,198	96,773	497,116	156,751
Total changes in fair value included in income	297,198	96,773	497,116	156,751
Transfers from interest rate lock commitments to loans held for sale	(740,477)	(170,942)	(1,103,831)	(271,176)
Balance at the end of the period	368,064	111,776	368,064	111,776
Changes in fair value recognized during the period relating to assets still held at the end of the period	368,064	111,776	368,064	111,776
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	24,632	8,187	26,770
Purchases and issuances, net		3,662		13,517
Sales and repayments		(11,136)		(22,572)
Changes in fair value included in income arising from:
Other factors		(1,143)		(1,700)
Total changes in fair value included in income		(1,143)		(1,700)
Balance at the end of the period	8,187	16,015	8,187	16,015
Changes in fair value recognized during the period relating to assets still held at the end of the period		244		244
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	2,193,697	2,905,090	2,926,790	2,820,612
Purchases and issuances, net		(373)	25,760	227,399
Mortgage servicing rights resulting from loan sales	225,534	183,331	507,849	299,082
Changes in fair value included in income arising from:
Other factors	(205,692)	(367,713)	(1,246,860)	(626,758)
Total changes in fair value included in income	(205,692)	(367,713)	(1,246,860)	(626,758)
Balance at the end of the period	2,213,539	2,720,335	2,213,539	2,720,335
Changes in fair value recognized during the period relating to assets still held at the end of the period	$ (205,692)	$ (367,713)	$ (1,246,860)	$ (626,758)