Allowance for Credit Losses - Disaggregated analysis of the changes in allowance for credit losses (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Jun. 07, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Allowance for credit losses
Balance at beginning of period		$ 434,608	$ 58,213	$ 56,927	$ 55,798
Charge-offs		(4,642)	(2,779)	(10,296)	(7,260)
Recoveries		4,048	884	8,287	2,833
Net charge-offs		(594)	(1,895)	(2,009)	(4,427)
Provision (benefit)		7,687	4,028	71,957	9,220
Balance at end of period		440,159	60,255	440,159	60,255
Quantitative allowance
Collectively evaluated		426,934		426,934
Individually evaluated		1,171		1,171
Total quantitative allowance		428,105		428,105
Qualitative allowance		12,054		12,054
Provision for loan losses charged to operations		7,687	$ 4,028	71,957	$ 9,220
Unfunded Commitment
Allowance for credit losses
Provision (benefit)		22,100		36,400
Quantitative allowance
Provision for loan losses charged to operations		22,100		36,400
Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period		1,542		3,408
Balance at end of period		149,404		149,404
Adjustments
Allowance for credit losses
Balance at beginning of period		433,066		111,365
Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period				51,030
Balance at end of period		109,442		109,442
Mortgage
Allowance for credit losses
Balance at beginning of period		67,342		6,128
Charge-offs		(90)		(473)
Recoveries		289		876
Net charge-offs		199		403
Provision (benefit)		(5,351)		3,180
Balance at end of period		62,219		62,219
Quantitative allowance
Collectively evaluated		60,377		60,377
Individually evaluated		115		115
Total quantitative allowance		60,492		60,492
Qualitative allowance		1,727		1,727
Provision for loan losses charged to operations		(5,351)		3,180
Mortgage | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period		29		406
Balance at end of period		29,935		29,935
Mortgage | Adjustments
Allowance for credit losses
Balance at beginning of period		67,371		11,989
Mortgage | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period				5,455
Balance at end of period		16,712		16,712
HELOC
Allowance for credit losses
Balance at beginning of period		1,081		15
Charge-offs				(24)
Recoveries		100		246
Net charge-offs		100		222
Provision (benefit)		253		153
Balance at end of period		1,434		1,434
Quantitative allowance
Collectively evaluated		1,477		1,477
Total quantitative allowance		1,477		1,477
Qualitative allowance		(43)		(43)
Provision for loan losses charged to operations		253		153
HELOC | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period				3
Balance at end of period		804		804
HELOC | Adjustments
Allowance for credit losses
Balance at beginning of period		1,081		29
HELOC | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period				11
Balance at end of period		226		226
Non MOHO
Allowance for credit losses
Balance at beginning of period		26,623		4,327
Charge-offs		(297)		(978)
Recoveries		365		988
Net charge-offs		68		10
Provision (benefit)		(5,584)		3,286
Balance at end of period		21,107		21,107
Quantitative allowance
Collectively evaluated		18,868		18,868
Individually evaluated		73		73
Total quantitative allowance		18,941		18,941
Qualitative allowance		2,166		2,166
Provision for loan losses charged to operations		(5,584)		3,286
Non MOHO | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period				289
Balance at end of period		5,119		5,119
Non MOHO | Adjustments
Allowance for credit losses
Balance at beginning of period		26,623		8,465
Non MOHO | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period				3,849
Balance at end of period		4,227		4,227
Mobile Home
Allowance for credit losses
Balance at beginning of period		9,439		815
Charge-offs				(31)
Recoveries		79		83
Net charge-offs		79		52
Provision (benefit)		(4,151)		(2,474)
Balance at end of period		5,367		5,367
Quantitative allowance
Collectively evaluated		5,132		5,132
Total quantitative allowance		5,132		5,132
Qualitative allowance		235		235
Provision for loan losses charged to operations		(4,151)		(2,474)
Mobile Home | Initial PCD Allowance
Allowance for credit losses
Balance at end of period		1,302		1,302
Mobile Home | Adjustments
Allowance for credit losses
Balance at beginning of period		9,439		1,594
Mobile Home | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period				779
Balance at end of period		4,893		4,893
Ready Reserves
Allowance for credit losses
Balance at beginning of period		33,912		6,211
Charge-offs		(38)		(212)
Recoveries		221		1,070
Net charge-offs		183		858
Provision (benefit)		29,756		37,135
Balance at end of period		63,851		63,851
Quantitative allowance
Collectively evaluated		66,087		66,087
Individually evaluated		8		8
Total quantitative allowance		66,095		66,095
Qualitative allowance		(2,244)		(2,244)
Provision for loan losses charged to operations		29,756		37,135
Ready Reserves | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period				351
Balance at end of period		6,035		6,035
Ready Reserves | Adjustments
Allowance for credit losses
Balance at beginning of period		33,912		12,150
Ready Reserves | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period				5,588
Balance at end of period		7,673		7,673
Overdrafts
Allowance for credit losses
Balance at beginning of period		20,170		4,350
Charge-offs		(1,393)		(4,301)
Recoveries		602		1,498
Net charge-offs		(791)		(2,803)
Provision (benefit)		4,577		8,294
Balance at end of period		23,956		23,956
Quantitative allowance
Collectively evaluated		19,276		19,276
Individually evaluated		2		2
Total quantitative allowance		19,278		19,278
Qualitative allowance		4,678		4,678
Provision for loan losses charged to operations		4,577		8,294
Overdrafts | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period				669
Balance at end of period		6,120		6,120
Overdrafts | Adjustments
Allowance for credit losses
Balance at beginning of period		20,170		8,509
Overdrafts | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period				3,490
Balance at end of period		3,836		3,836
Land
Allowance for credit losses
Balance at beginning of period		7,792		1,557
Recoveries		8		63
Net charge-offs		8		63
Provision (benefit)		767		3,345
Balance at end of period		8,567		8,567
Quantitative allowance
Collectively evaluated		8,567		8,567
Total quantitative allowance		8,567		8,567
Provision for loan losses charged to operations		767		3,345
Land | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period				97
Balance at end of period		902		902
Land | Adjustments
Allowance for credit losses
Balance at beginning of period		7,792		3,045
Land | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period				1,391
Balance at end of period		1,212		1,212
CRE-OO and C&I
Allowance for credit losses
Balance at beginning of period		4,075		956
Provision (benefit)		(2,641)		(2,358)
Balance at end of period		1,434		1,434
Quantitative allowance
Collectively evaluated		603		603
Total quantitative allowance		603		603
Qualitative allowance		831		831
Provision for loan losses charged to operations		(2,641)		(2,358)
CRE-OO and C&I | Initial PCD Allowance
Allowance for credit losses
Balance at end of period		1,003		1,003
CRE-OO and C&I | Adjustments
Allowance for credit losses
Balance at beginning of period		4,075		1,870
CRE-OO and C&I | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period				914
Balance at end of period		919		919
CRE and OIPP
Allowance for credit losses
Balance at beginning of period		90,206		10,879
Charge-offs		(458)		(1,081)
Recoveries		457		885
Net charge-offs		(1)		(196)
Provision (benefit)		4,830		13,224
Balance at end of period		93,780		93,780
Quantitative allowance
Collectively evaluated		95,399		95,399
Individually evaluated		961		961
Total quantitative allowance		96,360		96,360
Qualitative allowance		(2,580)		(2,580)
Provision for loan losses charged to operations		4,830		13,224
CRE and OIPP | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period		1,255		898
Balance at end of period		34,077		34,077
CRE and OIPP | Adjustments
Allowance for credit losses
Balance at beginning of period		88,951		21,282
CRE and OIPP | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period				9,505
Balance at end of period		25,393		25,393
BEX and Micro
Allowance for credit losses
Balance at beginning of period		129,958		15,219
Charge-offs		(578)		(601)
Recoveries		234		287
Net charge-offs		(344)		(314)
Provision (benefit)		(9,181)		10,123
Balance at end of period		120,436		120,436
Quantitative allowance
Collectively evaluated		121,403		121,403
Individually evaluated		5		5
Total quantitative allowance		121,408		121,408
Qualitative allowance		(972)		(972)
Provision for loan losses charged to operations		(9,181)		10,123
BEX and Micro | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period		3		656
Balance at end of period		45,787		45,787
BEX and Micro | Adjustments
Allowance for credit losses
Balance at beginning of period		129,961		29,773
BEX and Micro | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period				13,898
Balance at end of period		35,067		35,067
In transit/Other
Allowance for credit losses
Balance at beginning of period		44,010		6,470
Charge-offs		(1,788)		(2,595)
Recoveries		1,693		2,291
Net charge-offs		(95)		(304)
Provision (benefit)		(5,588)		(1,951)
Balance at end of period		38,008		38,008
Quantitative allowance
Collectively evaluated		29,745		29,745
Individually evaluated		7		7
Total quantitative allowance		29,752		29,752
Qualitative allowance		8,256		8,256
Provision for loan losses charged to operations		(5,588)		(1,951)
In transit/Other | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period		319		39
Balance at end of period		18,320		18,320
In transit/Other | Adjustments
Allowance for credit losses
Balance at beginning of period		43,691		12,659
In transit/Other | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period				6,150
Balance at end of period		$ 9,284		9,284
CSFL
Allowance for credit losses
Charge-offs	$ (158,200)
CSFL | Unfunded Commitment
Allowance for credit losses
Provision (benefit)				9,600
Quantitative allowance
Provision for loan losses charged to operations				$ 9,600