Fair Value - Level 3 Input Roll Forward, Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Mortgage servicing liabilities resulting from loan sales			$ 6,576	$ 27,133
Recurring basis
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	$ 3,251,509	$ 3,066,124	3,455,505	3,156,728
Purchases and issuances, net	3,327,099	2,062,591	6,121,075	4,155,778
Capitalization of interest and advances	22,262		55,283
Sales and repayments	(97,225)	(1,591,986)	(896,517)	(2,446,893)
Mortgage servicing rights resulting from loan sales	245,946	246,757	753,795	545,839
Changes in fair value included in income arising from:
Changes in instrument specific credit risk	42,029	4,252	35,638	(2,025)
Other factors	186,496	(318,655)	(563,248)	(790,362)
Total changes in fair value included in income	228,525	(314,403)	(527,610)	(792,387)
Transfers from mortgage loans held for sale from Level 3 to Level 2	(597,134)	(416,062)	(1,476,027)	(1,292,824)
Transfers to real estate acquired in settlement of loans		(376)	(691)	(2,420)
Reinstatement from real estate acquired in settlement of loans	755		755
Transfers from interest rate lock commitments to loans held for sale	(731,474)	(258,064)	(1,835,305)	(529,240)
Balance at the end of the period	5,650,263	2,794,581	5,650,263	2,794,581
Changes in fair value recognized during the period relating to assets still held at the end of the period	454,285	(268,048)	(799,403)	(894,832)
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	181,064	207,104	207,726	224,791
Issuances	531	377	1,393	1,327
Accrual of interest on excess servicing spread financing	2,070	2,291	6,416	8,124
Repayment	(7,682)	(9,819)	(25,112)	(30,901)
Mortgage servicing liabilities resulting from loan sales		19,501	6,576	27,133
Changes in fair value included in income	(1,295)	(2,019)	(22,311)	(13,039)
Balance at the end of the period	174,688	217,435	174,688	217,435
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	(1,295)	(2,019)	(22,311)	(13,039)
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	151,206	194,156	178,586	216,110
Issuances	531	377	1,393	1,327
Accrual of interest on excess servicing spread financing	2,070	2,291	6,416	8,124
Repayment	(7,682)	(9,819)	(25,112)	(30,901)
Changes in fair value included in income	(3,135)	(3,864)	(18,293)	(11,519)
Balance at the end of the period	142,990	183,141	142,990	183,141
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	(3,135)	(3,864)	(18,293)	(11,519)
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	29,858	12,948	29,140	8,681
Mortgage servicing liabilities resulting from loan sales		19,501	6,576	27,133
Changes in fair value included in income	1,840	1,845	(4,018)	(1,520)
Balance at the end of the period	31,698	34,294	31,698	34,294
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	1,840	1,845	(4,018)	(1,520)
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	661,719	217,998	383,878	260,008
Purchases and issuances, net	2,734,321	1,861,769	4,664,408	3,537,177
Capitalization of interest and advances	22,262		55,283
Sales and repayments	(88,955)	(1,582,564)	(888,247)	(2,414,899)
Changes in fair value included in income arising from:
Changes in instrument specific credit risk	42,029	4,252	35,638	(2,025)
Total changes in fair value included in income	42,029	4,252	35,638	(2,025)
Transfers from mortgage loans held for sale from Level 3 to Level 2	(597,134)	(416,062)	(1,476,027)	(1,292,824)
Transfers to real estate acquired in settlement of loans		(376)	(691)	(2,420)
Reinstatement from real estate acquired in settlement of loans	755		755
Balance at the end of the period	2,774,997	85,017	2,774,997	85,017
Changes in fair value recognized during the period relating to assets still held at the end of the period	38,217	(2,328)	31,389	(2,478)
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	368,064	111,776	136,650	49,338
Purchases and issuances, net	593,065	199,274	1,431,194	376,137
Changes in fair value included in income arising from:
Other factors	311,790	92,138	808,906	248,889
Total changes in fair value included in income	311,790	92,138	808,906	248,889
Transfers from interest rate lock commitments to loans held for sale	(731,474)	(258,064)	(1,835,305)	(529,240)
Balance at the end of the period	541,445	145,124	541,445	145,124
Changes in fair value recognized during the period relating to assets still held at the end of the period	541,445	145,124	541,445	145,124
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	16,015	8,187	26,770
Purchases and issuances, net		1,502		15,019
Sales and repayments	(8,270)	(9,422)	(8,270)	(31,994)
Changes in fair value included in income arising from:
Other factors	83	92	83	(1,608)
Total changes in fair value included in income	83	92	83	(1,608)
Balance at the end of the period		8,187		8,187
Changes in fair value recognized during the period relating to assets still held at the end of the period		41		165
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	2,213,539	2,720,335	2,926,790	2,820,612
Purchases and issuances, net	(287)	46	25,473	227,445
Mortgage servicing rights resulting from loan sales	245,946	246,757	753,795	545,839
Changes in fair value included in income arising from:
Other factors	(125,377)	(410,885)	(1,372,237)	(1,037,643)
Total changes in fair value included in income	(125,377)	(410,885)	(1,372,237)	(1,037,643)
Balance at the end of the period	2,333,821	2,556,253	2,333,821	2,556,253
Changes in fair value recognized during the period relating to assets still held at the end of the period	$ (125,377)	$ (410,885)	$ (1,372,237)	$ (1,037,643)