Fair Value - Level 3 Input Roll Forward, Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2018
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Mortgage servicing liabilities resulting from loan sales			$ 27,133	$ 5,548
Excess servicing spread financing
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	$ 194,156	$ 229,470	216,110	236,534
Accrual of interest on excess servicing spread financing	2,291	3,740	8,124	11,584
Repayment	(9,819)	(11,543)	(30,901)	(35,852)
Changes in fair value included in income	(3,864)	1,109	(11,519)	9,026
Balance at the end of the period	183,141	223,275	183,141	223,275
Recurring basis
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	3,066,124	2,901,793	3,156,728	1,489,149
Reclassification of mortgage servicing rights previously accounted for under the amortization method					$ 1,482,426
Balance after reclassification					2,971,575
Purchases				2,868,436
Purchases and issuances, net	2,062,591	1,226,797	4,155,778
Sales and repayments	(1,591,986)	(243,903)	(2,446,893)	(1,141,908)
Mortgage servicing rights resulting from loan sales	246,757	149,000	545,839	448,604
Changes in fair value included in income arising from:
Changes in instrument specific credit risk	4,252	84	(2,025)	(4,944)
Other factors	(318,655)	(2,235)	(790,362)	(6,688)
Total changes in fair value included in income	(314,403)	(2,151)	(792,387)	(11,632)
Transfers from mortgage loans held for sale from Level 3 to Level 2	(416,062)	(744,324)	(1,292,824)	(1,765,854)
Transfers to real estate acquired in settlement of loans	(376)	(1,364)	(2,420)	(4,185)
Transfers from interest rate lock commitments to loans held for sale	(258,064)	(70,943)	(529,240)	(150,131)
Balance at the end of the period	2,794,581	3,214,905	2,794,581	3,214,905
Changes in fair value recognized during the period relating to assets still held at the end of the period	(268,048)	19,648	(894,832)	55,535
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Balance at the beginning of the period	207,104	239,723	224,791	250,654
Issuances	377	499	1,327	1,983
Accrual of interest on excess servicing spread financing	2,291	3,740	8,124	11,584
Repayment	(9,819)	(11,543)	(30,901)	(35,852)
Mortgage servicing liabilities resulting from loan sales	19,501	1,741	27,133	5,548
Changes in fair value included in income	(2,019)	(1,116)	(13,039)	(873)
Balance at the end of the period	217,435	233,044	217,435	233,044
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	(2,019)	(1,116)	(13,039)	(873)
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	194,156	229,470	216,110	236,534
Issuances	377	499	1,327	1,983
Accrual of interest on excess servicing spread financing	2,291	3,740	8,124	11,584
Repayment	(9,819)	(11,543)	(30,901)	(35,852)
Changes in fair value included in income	(3,864)	1,109	(11,519)	9,026
Balance at the end of the period	183,141	223,275	183,141	223,275
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	(3,864)	1,109	(11,519)	9,026
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	12,948	10,253	8,681	14,120
Mortgage servicing liabilities resulting from loan sales	19,501	1,741	27,133	5,548
Changes in fair value included in income	1,845	(2,225)	(1,520)	(9,899)
Balance at the end of the period	34,294	9,769	34,294	9,769
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	1,845	(2,225)	(1,520)	(9,899)
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	217,998	334,166	260,008	782,211
Balance after reclassification					782,211
Purchases				2,480,523
Purchases and issuances, net	1,861,769	1,008,662	3,537,177
Sales and repayments	(1,582,564)	(231,921)	(2,414,899)	(1,122,448)
Changes in fair value included in income arising from:
Changes in instrument specific credit risk	4,252	84	(2,025)	(4,944)
Total changes in fair value included in income	4,252	84	(2,025)	(4,944)
Transfers from mortgage loans held for sale from Level 3 to Level 2	(416,062)	(744,324)	(1,292,824)	(1,765,854)
Transfers to real estate acquired in settlement of loans	(376)	(1,364)	(2,420)	(4,185)
Balance at the end of the period	85,017	365,303	85,017	365,303
Changes in fair value recognized during the period relating to assets still held at the end of the period	(2,328)	(4,811)	(2,478)	(4,912)
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	111,776	55,689	49,338	58,272
Balance after reclassification					58,272
Purchases				157,649
Purchases and issuances, net	199,274	41,721	376,137
Changes in fair value included in income arising from:
Other factors	92,138	10,696	248,889	(28,627)
Total changes in fair value included in income	92,138	10,696	248,889	(28,627)
Transfers from interest rate lock commitments to loans held for sale	(258,064)	(70,943)	(529,240)	(150,131)
Balance at the end of the period	145,124	37,163	145,124	37,163
Changes in fair value recognized during the period relating to assets still held at the end of the period	145,124	37,163	145,124	37,163
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	16,015	25,781	26,770	10,656
Balance after reclassification					10,656
Purchases				36,624
Purchases and issuances, net	1,502	12,903	15,019
Sales and repayments	(9,422)	(11,982)	(31,994)	(19,460)
Changes in fair value included in income arising from:
Other factors	92	(227)	(1,608)	(1,345)
Total changes in fair value included in income	92	(227)	(1,608)	(1,345)
Balance at the end of the period	8,187	26,475	8,187	26,475
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	2,720,335	2,486,157	2,820,612	638,010
Reclassification of mortgage servicing rights previously accounted for under the amortization method					1,482,426
Balance after reclassification					$ 2,120,436
Purchases				193,640
Purchases and issuances, net	46	163,511	227,445
Mortgage servicing rights resulting from loan sales	246,757	149,000	545,839	448,604
Changes in fair value included in income arising from:
Other factors	(410,885)	(12,704)	(1,037,643)	23,284
Total changes in fair value included in income	(410,885)	(12,704)	(1,037,643)	23,284
Balance at the end of the period	2,556,253	2,785,964	2,556,253	2,785,964
Changes in fair value recognized during the period relating to assets still held at the end of the period	$ (410,885)	$ (12,704)	$ (1,037,643)	$ 23,284