Derivative Activities - Other Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Derivative assets:
Derivative asset, before netting				$ 187,397	$ 123,316
Netting				(27,711)	(26,969)
Total derivative assets				159,686	96,347
Derivative liabilities:
Derivative liability, before netting				38,946	28,146
Netting				(16,616)	(25,082)
Net amounts of liabilities presented in the consolidated balance sheet				22,330	3,064
Interest Expense. | Repurchase agreement derivative
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Gains (losses) recognized on derivative financial instruments	$ (1,609)	$ (1,704)	$ (330)
Net gains on loans held for sale at fair value | Interest rate lock commitments and loans held for sale
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Gains (losses) recognized on derivative financial instruments	(157,806)	81,522	(21,255)
Net loan servicing fees | Mortgage servicing rights
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Gains (losses) recognized on derivative financial instruments	395,497	(121,045)	(37,855)
Margin Deposits
Derivative assets:
Collateral placed with (received from) derivative counterparties				(11,095)	(1,887)
Interest rate lock commitments
Derivative assets:
Total derivative assets				138,511	50,507
Interest rate lock commitments | Net gains on loans held for sale at fair value
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Gains (losses) recognized on derivative financial instruments	87,312	(8,934)	(1,120)
Not designated as hedging instrument | Repurchase agreement derivatives
Derivative assets:
Derivative asset, before netting				8,187	26,770
Not designated as hedging instrument | Interest rate lock commitments
Derivative Instruments
Notional amount	7,122,316	2,805,400		7,122,316	2,805,400
Derivative assets:
Derivative asset, before netting				138,511	50,507
Derivative liabilities:
Derivative liability, before netting				1,861	1,169
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Balance at beginning of period	2,805,400
Balance at end of period	7,122,316	2,805,400
Not designated as hedging instrument | Forward contracts | Purchases
Derivative Instruments
Notional amount	13,618,361	6,657,026	4,920,883	13,618,361	6,657,026
Derivative assets:
Derivative asset, before netting				12,364	35,916
Derivative liabilities:
Derivative liability, before netting				19,040	215
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Balance at beginning of period	6,657,026	4,920,883	12,746,191
Additions	331,273,011	184,780,152	181,761,564
Dispositions/expirations	(324,311,676)	(183,044,009)	(189,586,872)
Balance at end of period	13,618,361	6,657,026	4,920,883
Not designated as hedging instrument | Forward contracts | Sales
Derivative Instruments
Notional amount	16,220,526	6,890,046	5,204,796	16,220,526	6,890,046
Derivative assets:
Derivative asset, before netting				17,097	437
Derivative liabilities:
Derivative liability, before netting				18,045	26,762
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Balance at beginning of period	6,890,046	5,204,796	16,577,942
Additions	395,584,533	230,735,936	226,000,107
Dispositions/expirations	(386,254,053)	(229,050,686)	(237,373,253)
Balance at end of period	16,220,526	6,890,046	5,204,796
Not designated as hedging instrument | MBS put options
Derivative Instruments
Notional amount	6,100,000	4,635,000	4,925,000	6,100,000	4,635,000
Derivative assets:
Derivative asset, before netting				3,415	720
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Balance at beginning of period	4,635,000	4,925,000	1,175,000
Additions	97,035,000	31,085,000	25,050,000
Dispositions/expirations	(95,570,000)	(31,375,000)	(21,300,000)
Balance at end of period	6,100,000	4,635,000	4,925,000
Not designated as hedging instrument | MBS call options
Derivative Instruments
Notional amount	1,450,000	1,450,000	1,600,000		1,450,000
Derivative assets:
Derivative asset, before netting					2,135
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Balance at beginning of period	1,450,000		1,600,000
Additions	6,750,000	14,325,000	17,700,000
Dispositions/expirations	(8,200,000)	(12,875,000)	(19,300,000)
Balance at end of period		1,450,000
Not designated as hedging instrument | Swaptions
Derivative Instruments
Notional amount	1,750,000			1,750,000
Derivative assets:
Derivative asset, before netting				2,409
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Additions	1,750,000
Dispositions/expirations	0
Balance at end of period	1,750,000
Not designated as hedging instrument | Put options on interest rate futures | Purchases
Derivative Instruments
Notional amount	2,250,000	3,085,000	2,125,000	2,250,000	3,085,000
Derivative assets:
Derivative asset, before netting				3,945	866
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Balance at beginning of period	3,085,000	2,125,000	1,125,000
Additions	23,322,500	20,559,800	11,360,000
Dispositions/expirations	(24,157,500)	(19,599,800)	(10,360,000)
Balance at end of period	2,250,000	3,085,000	2,125,000
Not designated as hedging instrument | Put options on interest rate futures | Sales
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Additions	33,297,800	20,474,800	10,010,000
Dispositions/expirations	(33,297,800)	(20,474,800)	(10,010,000)
Not designated as hedging instrument | Call options on interest rate futures | Purchases
Derivative Instruments
Notional amount	750,000	1,512,500	100,000	750,000	1,512,500
Derivative assets:
Derivative asset, before netting				1,469	5,965
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Balance at beginning of period	1,512,500	100,000	900,000
Additions	14,377,800	4,387,500	1,939,300
Dispositions/expirations	(15,140,300)	(2,975,000)	(2,739,300)
Balance at end of period	750,000	1,512,500	100,000
Not designated as hedging instrument | Call options on interest rate futures | Sales
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Additions	5,937,500	2,100,000	2,739,300
Dispositions/expirations	(5,937,500)	(2,100,000)	(2,739,300)
Not designated as hedging instrument | Treasury future | Purchases
Derivative Instruments
Notional amount	1,276,000	835,000	100,000	1,276,000	835,000
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Balance at beginning of period	835,000	100,000
Additions	14,344,400	9,837,500	544,900
Dispositions/expirations	(13,903,400)	(9,102,500)	(444,900)
Balance at end of period	1,276,000	835,000	100,000
Not designated as hedging instrument | Treasury future | Sales
Derivative Instruments
Notional amount	1,010,000	1,450,000		1,010,000	1,450,000
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Balance at beginning of period	1,450,000
Additions	13,463,400	11,213,800	444,900
Dispositions/expirations	(13,903,400)	(9,763,800)	(444,900)
Balance at end of period	1,010,000	1,450,000
Not designated as hedging instrument | Interest rate swap futures | Purchases
Derivative Instruments
Notional amount	3,210,000	625,000	1,400,000	$ 3,210,000	$ 625,000
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Balance at beginning of period	625,000	1,400,000	200,000
Additions	5,300,000	1,510,000	2,100,000
Dispositions/expirations	(2,715,000)	(2,285,000)	(900,000)
Balance at end of period	3,210,000	625,000	1,400,000
Not designated as hedging instrument | Interest rate swap futures | Sales
Activity for derivative contracts used to hedge the IRLCs and inventory of mortgage loans at notional value
Additions	2,715,000	2,285,000	900,000
Dispositions/expirations	$ (2,715,000)	$ (2,285,000)	$ (900,000)