Allowance for Credit Losses (ACL) - 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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Allowance for credit losses
Balance at beginning of period		$ 350,401	$ 434,608	$ 457,309	$ 56,927
Charge-offs		(3,847)	(4,642)	(12,883)	(10,296)
Recoveries		3,801	4,048	10,744	8,287
Net (charge-offs) recoveries		(46)	(594)	(2,139)	(2,009)
(Recovery) provision		(36,211)	7,687	(141,026)	71,957
Balance at end of period		314,144	440,159	314,144	440,159
Quantitative allowance
Collectively evaluated		297,728	426,934	297,728	426,934
Individually evaluated		1,726	1,171	1,726	1,171
Total quantitative allowance		299,454	428,105	299,454	428,105
Qualitative allowance		14,690	12,054	14,690	12,054
Provision for credit losses		(36,211)	7,687	(141,026)	71,957
Unfunded Commitment
Allowance for credit losses
(Recovery) provision		(2,700)	22,100	(15,100)	36,400
Quantitative allowance
Provision for credit losses		(2,700)	22,100	(15,100)	36,400
Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period					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			(1,542)		51,030
Balance at end of period			109,442		109,442
Residential Mortgage Sr.
Allowance for credit losses
Balance at beginning of period		55,820	67,342	63,561	6,128
Charge-offs		(15)	(90)	(204)	(473)
Recoveries		332	289	1,103	876
Net (charge-offs) recoveries		317	199	899	403
(Recovery) provision		(4,587)	(5,351)	(12,910)	3,180
Balance at end of period		51,550	62,219	51,550	62,219
Quantitative allowance
Collectively evaluated		48,411	60,377	48,411	60,377
Individually evaluated		77	115	77	115
Total quantitative allowance		48,488	60,492	48,488	60,492
Qualitative allowance		3,062	1,727	3,062	1,727
Provision for credit losses		(4,587)	(5,351)	(12,910)	3,180
Residential Mortgage Sr. | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period					406
Balance at end of period			29,935		29,935
Residential Mortgage Sr. | Adjustments
Allowance for credit losses
Balance at beginning of period			67,371		11,989
Residential Mortgage Sr. | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period			29		5,455
Balance at end of period			16,712		16,712
Residential Mortgage Jr.
Allowance for credit losses
Balance at beginning of period		825	1,081	1,238	15
Charge-offs					(24)
Recoveries		48	100	131	246
Net (charge-offs) recoveries		48	100	131	222
(Recovery) provision		(174)	253	(670)	153
Balance at end of period		699	1,434	699	1,434
Quantitative allowance
Collectively evaluated		699	1,477	699	1,477
Total quantitative allowance		699	1,477	699	1,477
Qualitative allowance			(43)		(43)
Provision for credit losses		(174)	253	(670)	153
Residential Mortgage Jr. | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period					3
Balance at end of period			804		804
Residential Mortgage Jr. | Adjustments
Allowance for credit losses
Balance at beginning of period			1,081		29
Residential Mortgage Jr. | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period					11
Balance at end of period			226		226
HELOC
Allowance for credit losses
Balance at beginning of period		14,550	26,623	16,698	4,327
Charge-offs		(149)	(297)	(835)	(978)
Recoveries		720	365	1,903	988
Net (charge-offs) recoveries		571	68	1,068	10
(Recovery) provision		(204)	(5,584)	(2,849)	3,286
Balance at end of period		14,917	21,107	14,917	21,107
Quantitative allowance
Collectively evaluated		13,307	18,868	13,307	18,868
Individually evaluated		959	73	959	73
Total quantitative allowance		14,266	18,941	14,266	18,941
Qualitative allowance		651	2,166	651	2,166
Provision for credit losses		(204)	(5,584)	(2,849)	3,286
HELOC | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period					289
Balance at end of period			5,119		5,119
HELOC | Adjustments
Allowance for credit losses
Balance at beginning of period			26,623		8,465
HELOC | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period					3,849
Balance at end of period			4,227		4,227
Residential Construction
Allowance for credit losses
Balance at beginning of period		4,488	9,439	4,914	815
Charge-offs					(31)
Recoveries		2	79	3	83
Net (charge-offs) recoveries		2	79	3	52
(Recovery) provision		295	(4,151)	(132)	(2,474)
Balance at end of period		4,785	5,367	4,785	5,367
Quantitative allowance
Collectively evaluated		4,756	5,132	4,756	5,132
Total quantitative allowance		4,756	5,132	4,756	5,132
Qualitative allowance		29	235	29	235
Provision for credit losses		295	(4,151)	(132)	(2,474)
Residential Construction | Initial PCD Allowance
Allowance for credit losses
Balance at end of period			1,302		1,302
Residential Construction | Adjustments
Allowance for credit losses
Balance at beginning of period			9,439		1,594
Residential Construction | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period					779
Balance at end of period			4,893		4,893
Other C&D
Allowance for credit losses
Balance at beginning of period		45,488	33,912	67,197	6,211
Charge-offs			(38)	(87)	(212)
Recoveries		748	221	1,178	1,070
Net (charge-offs) recoveries		748	183	1,091	858
(Recovery) provision		(10,337)	29,756	(32,389)	37,135
Balance at end of period		35,899	63,851	35,899	63,851
Quantitative allowance
Collectively evaluated		35,893	66,087	35,893	66,087
Individually evaluated		6	8	6	8
Total quantitative allowance		35,899	66,095	35,899	66,095
Qualitative allowance			(2,244)		(2,244)
Provision for credit losses		(10,337)	29,756	(32,389)	37,135
Other C&D | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period					351
Balance at end of period			6,035		6,035
Other C&D | Adjustments
Allowance for credit losses
Balance at beginning of period			33,912		12,150
Other C&D | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period					5,588
Balance at end of period			7,673		7,673
Consumer
Allowance for credit losses
Balance at beginning of period		25,697	20,170	26,562	4,350
Charge-offs		(2,366)	(1,393)	(6,001)	(4,301)
Recoveries		577	602	1,618	1,498
Net (charge-offs) recoveries		(1,789)	(791)	(4,383)	(2,803)
(Recovery) provision		332	4,577	2,061	8,294
Balance at end of period		24,240	23,956	24,240	23,956
Quantitative allowance
Collectively evaluated		21,509	19,276	21,509	19,276
Individually evaluated			2		2
Total quantitative allowance		21,509	19,278	21,509	19,278
Qualitative allowance		2,731	4,678	2,731	4,678
Provision for credit losses		332	4,577	2,061	8,294
Consumer | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period					669
Balance at end of period			6,120		6,120
Consumer | Adjustments
Allowance for credit losses
Balance at beginning of period			20,170		8,509
Consumer | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period					3,490
Balance at end of period			3,836		3,836
Multifamily
Allowance for credit losses
Balance at beginning of period		5,883	7,792	7,887	1,557
Recoveries			8	3	63
Net (charge-offs) recoveries			8	3	63
(Recovery) provision		(1,299)	767	(3,306)	3,345
Balance at end of period		4,584	8,567	4,584	8,567
Quantitative allowance
Collectively evaluated		4,584	8,567	4,584	8,567
Total quantitative allowance		4,584	8,567	4,584	8,567
Provision for credit losses		(1,299)	767	(3,306)	3,345
Multifamily | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period					97
Balance at end of period			902		902
Multifamily | Adjustments
Allowance for credit losses
Balance at beginning of period			7,792		3,045
Multifamily | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period					1,391
Balance at end of period			1,212		1,212
Municipal
Allowance for credit losses
Balance at beginning of period		1,063	4,075	1,510	956
(Recovery) provision		(554)	(2,641)	(1,001)	(2,358)
Balance at end of period		509	1,434	509	1,434
Quantitative allowance
Collectively evaluated		509	603	509	603
Total quantitative allowance		509	603	509	603
Qualitative allowance			831		831
Provision for credit losses		(554)	(2,641)	(1,001)	(2,358)
Municipal | Initial PCD Allowance
Allowance for credit losses
Balance at end of period			1,003		1,003
Municipal | Adjustments
Allowance for credit losses
Balance at beginning of period			4,075		1,870
Municipal | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period					914
Balance at end of period			919		919
CRE Owner Occupied
Allowance for credit losses
Balance at beginning of period		75,492	90,206	97,104	10,879
Charge-offs		(4)	(458)	(2,052)	(1,081)
Recoveries		332	457	796	885
Net (charge-offs) recoveries		328	(1)	(1,256)	(196)
(Recovery) provision		(10,611)	4,830	(30,639)	13,224
Balance at end of period		65,209	93,780	65,209	93,780
Quantitative allowance
Collectively evaluated		62,969	95,399	62,969	95,399
Individually evaluated		377	961	377	961
Total quantitative allowance		63,346	96,360	63,346	96,360
Qualitative allowance		1,863	(2,580)	1,863	(2,580)
Provision for credit losses		(10,611)	4,830	(30,639)	13,224
CRE Owner Occupied | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period					898
Balance at end of period			34,077		34,077
CRE Owner Occupied | Adjustments
Allowance for credit losses
Balance at beginning of period			88,951		21,282
CRE Owner Occupied | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period			(1,255)		9,505
Balance at end of period			25,393		25,393
Non Owner Occupied CRE
Allowance for credit losses
Balance at beginning of period		90,404	129,958	124,421	15,219
Charge-offs		(241)	(578)	(776)	(601)
Recoveries		173	234	905	287
Net (charge-offs) recoveries		(68)	(344)	129	(314)
(Recovery) provision		(7,458)	(9,181)	(41,672)	10,123
Balance at end of period		82,878	120,436	82,878	120,436
Quantitative allowance
Collectively evaluated		79,302	121,403	79,302	121,403
Individually evaluated			5		5
Total quantitative allowance		79,302	121,408	79,302	121,408
Qualitative allowance		3,576	(972)	3,576	(972)
Provision for credit losses		(7,458)	(9,181)	(41,672)	10,123
Non Owner Occupied CRE | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period					656
Balance at end of period			45,787		45,787
Non Owner Occupied CRE | Adjustments
Allowance for credit losses
Balance at beginning of period			129,961		29,773
Non Owner Occupied CRE | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period			3		13,898
Balance at end of period			35,067		35,067
C & I
Allowance for credit losses
Balance at beginning of period		30,691	44,010	46,217	6,470
Charge-offs		(1,072)	(1,788)	(2,928)	(2,595)
Recoveries		869	1,693	3,104	2,291
Net (charge-offs) recoveries		(203)	(95)	176	(304)
(Recovery) provision		(1,614)	(5,588)	(17,519)	(1,951)
Balance at end of period		28,874	38,008	28,874	38,008
Quantitative allowance
Collectively evaluated		25,789	29,745	25,789	29,745
Individually evaluated		307	7	307	7
Total quantitative allowance		26,096	29,752	26,096	29,752
Qualitative allowance		2,778	8,256	2,778	8,256
Provision for credit losses		$ (1,614)	(5,588)	$ (17,519)	(1,951)
C & I | Initial PCD Allowance
Allowance for credit losses
Balance at beginning of period					39
Balance at end of period			18,320		18,320
C & I | Adjustments
Allowance for credit losses
Balance at beginning of period			43,691		12,659
C & I | Adjustments | ASU 2016-13
Allowance for credit losses
Balance at beginning of period			(319)		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
(Recovery) provision					9,600
Quantitative allowance
Provision for credit losses					$ 9,600