Fair Value - Level 3 Input Roll Forward, Recurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Mortgage servicing liabilities resulting from loan sales	$ 37,988	$ 7,601	$ 17,229
Excess servicing spread financing
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Balance at the beginning of the year	216,110	236,534	288,669
Accrual of interest on excess servicing spread financing	10,291	15,138	16,951
Repayment	(40,316)	(46,750)	(54,980)
Changes in fair value included in income	(9,256)	8,500	(19,350)
Balance at the end of the year	178,586	216,110	236,534
Recurring basis
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the year	3,156,728	1,489,149	622,587
Reclassification of mortgage servicing rights previously accounted for under the amortization method			1,482,426
Balance after reclassification			2,971,575
Purchases and issuances, net	5,976,266	3,455,544	3,425,474
Capitalization of interest and advances	72,302
Sales and repayments	(3,488,849)	(1,392,574)	(1,339,580)
Mortgage servicing rights resulting from loan sales	884,876	591,757	24,471
Changes in fair value included in income arising from:
Changes in instrument specific credit risk	(6,332)	158	(1,794)
Other factors	(676,685)	(129,803)	28,868
Total changes in fair value included in income	(683,017)	(129,645)	27,074
Transfers from mortgage loans held for sale from Level 3 to Level 2	(1,646,554)	(2,128,551)	(851,935)
Transfers to real estate acquired in settlement of loans	(2,420)	(5,185)
Transfers from interest rate lock commitments to loans held for sale	(813,827)	(206,193)	(418,942)
Balance at the end of the year	3,455,505	3,156,728	1,489,149
Changes in fair value recognized during the period relating to assets still held at the end of the period	(875,083)	(80,309)	(28,850)
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Balance at the beginning of the year	224,791	250,654	303,861
Issuances	1,757	2,688	5,244
Accrual of interest on excess servicing spread financing	10,291	15,138	16,951
Repayment	(40,316)	(46,750)	(54,980)
Mortgage servicing liabilities resulting from mortgage loan sales	37,988
Mortgage servicing liabilities resulting from loan sales		7,601	17,229
Changes in fair value included in income	(26,785)	(4,540)	(37,651)
Balance at the end of the year	207,726	224,791	250,654
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	(26,785)	(4,540)	(37,651)
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 year	216,110	236,534	288,669
Issuances	1,757	2,688	5,244
Accrual of interest on excess servicing spread financing	10,291	15,138	16,951
Repayment	(40,316)	(46,750)	(54,980)
Changes in fair value included in income	(9,256)	8,500	(19,350)
Balance at the end of the year	178,586	216,110	236,534
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	(9,256)	8,500	(19,350)
Recurring basis | Mortgage servicing liabilities
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Balance at the beginning of the year	8,681	14,120	15,192
Mortgage servicing liabilities resulting from mortgage loan sales	37,988
Mortgage servicing liabilities resulting from loan sales		7,601	17,229
Changes in fair value included in income	(17,529)	(13,040)	(18,301)
Balance at the end of the year	29,140	8,681	14,120
Changes in fair value recognized during the period relating to liability still outstanding at the end of the period	(17,529)	(13,040)	(18,301)
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 year	260,008	782,211	47,271
Balance after reclassification			782,211
Purchases and issuances, net	5,163,730	2,972,042	2,928,249
Capitalization of interest and advances	72,302
Sales and repayments	(3,456,856)	(1,360,667)	(1,339,580)
Changes in fair value included in income arising from:
Changes in instrument specific credit risk	(6,332)	158	(1,794)
Total changes in fair value included in income	(6,332)	158	(1,794)
Transfers from mortgage loans held for sale from Level 3 to Level 2	(1,646,554)	(2,128,551)	(851,935)
Transfers to real estate acquired in settlement of loans	(2,420)	(5,185)
Balance at the end of the year	383,878	260,008	782,211
Changes in fair value recognized during the period relating to assets still held at the end of the period	(5,755)	(263)	(556)
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 year	49,338	58,272	59,391
Balance after reclassification			58,272
Purchases and issuances, net	570,072	195,974	302,389
Changes in fair value included in income arising from:
Other factors	331,067	1,285	115,434
Total changes in fair value included in income	331,067	1,285	115,434
Transfers from interest rate lock commitments to loans held for sale	(813,827)	(206,193)	(418,942)
Balance at the end of the year	136,650	49,338	58,272
Changes in fair value recognized during the period relating to assets still held at the end of the period	136,650	49,338	58,272
Recurring basis | Repurchase agreement derivatives
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the year	26,770	10,656
Balance after reclassification			10,656
Purchases and issuances, net	15,019	49,725	10,986
Sales and repayments	(31,993)	(31,907)
Changes in fair value included in income arising from:
Other factors	(1,609)	(1,704)	(330)
Total changes in fair value included in income	(1,609)	(1,704)	(330)
Balance at the end of the year	8,187	26,770	10,656
Changes in fair value recognized during the period relating to assets still held at the end of the period	165		(330)
Recurring basis | Mortgage servicing rights
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the year	2,820,612	638,010	515,925
Reclassification of mortgage servicing rights previously accounted for under the amortization method			1,482,426
Balance after reclassification			2,120,436
Purchases and issuances, net	227,445	237,803	183,850
Mortgage servicing rights resulting from loan sales	884,876	591,757	24,471
Changes in fair value included in income arising from:
Other factors	(1,006,143)	(129,384)	(86,236)
Total changes in fair value included in income	(1,006,143)	(129,384)	(86,236)
Balance at the end of the year	2,926,790	2,820,612	638,010
Changes in fair value recognized during the period relating to assets still held at the end of the period	$ (1,006,143)	$ (129,384)	$ (86,236)