ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY INFORMATION - Schedule of Allowance for Loan Losses and Loan Balances (Details) - USD ($) $ in Thousands		3 Months Ended
	Jan. 01, 2022	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCD loans allowance for credit losses at acquisition		$ 26,103
Allowance for credit losses
Beginning balance	$ 94,507	94,507	$ 228,804
Initial allowance on acquired PCD loans		26,103
Charge-offs		(4,851)	(5,476)
Recoveries		1,600	1,650
(Credit) provision		18,971	(20,160)
Ending balance		136,330	204,818
Period-end allowance allocated to:
Loans evaluated on an individual basis		6,992	12
Loans evaluated on a collective basis		129,338	204,806
Period-end loan balances:
Loans evaluated on an individual basis		50,166	38,334
Loans evaluated on a collective basis		11,279,362	8,530,808
Ending balance		11,329,528	8,569,142	$ 7,882,055
Reverse mortgage, fair value		4,300	9,400	3,900
Bryn Mawr Bank Corporation Acquisition
Accounts, Notes, Loans and Financing Receivable [Line Items]
Initial allowance on acquired PCD loans		49,600
Loans not purchased with credit deterioration		23,500
PCD loans allowance for credit losses at acquisition	26,103	26,100
Allowance for credit losses
Initial allowance on acquired PCD loans	26,103	26,100
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCD loans allowance for credit losses at acquisition		22,614
Allowance for credit losses
Beginning balance	49,967	49,967	150,875
Initial allowance on acquired PCD loans		22,614
Charge-offs		(3,639)	(5,052)
Recoveries		601	1,140
(Credit) provision		(3,827)	(21,093)
Ending balance		65,716	125,870
Period-end allowance allocated to:
Loans evaluated on an individual basis		6,987	1
Loans evaluated on a collective basis		58,729	125,869
Period-end loan balances:
Loans evaluated on an individual basis		27,735	20,902
Loans evaluated on a collective basis		2,956,392	2,642,570
Ending balance		2,984,127	2,663,472	2,270,319
Commercial | Owner-occupied commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCD loans allowance for credit losses at acquisition		595
Allowance for credit losses
Beginning balance	4,574	4,574	9,615
Initial allowance on acquired PCD loans		595
Charge-offs		(179)	0
Recoveries		126	90
(Credit) provision		1,009	(88)
Ending balance		6,125	9,617
Period-end allowance allocated to:
Loans evaluated on an individual basis		0	0
Loans evaluated on a collective basis		6,125	9,617
Period-end loan balances:
Loans evaluated on an individual basis		1,023	5,118
Loans evaluated on a collective basis		1,871,804	1,328,871
Ending balance		1,872,827	1,333,989	1,341,707
Commercial | Commercial mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCD loans allowance for credit losses at acquisition		2,684
Allowance for credit losses
Beginning balance	11,623	11,623	31,071
Initial allowance on acquired PCD loans		2,684
Charge-offs		(37)	0
Recoveries		121	14
(Credit) provision		8,714	(540)
Ending balance		23,105	30,545
Period-end allowance allocated to:
Loans evaluated on an individual basis		5	11
Loans evaluated on a collective basis		23,100	30,534
Period-end loan balances:
Loans evaluated on an individual basis		7,106	4,280
Loans evaluated on a collective basis		3,354,136	1,971,686
Ending balance		3,361,242	1,975,966	1,881,510
Commercial | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCD loans allowance for credit losses at acquisition		71
Allowance for credit losses
Beginning balance	1,903	1,903	12,190
Initial allowance on acquired PCD loans		71
Charge-offs		0	0
Recoveries		0	0
(Credit) provision		1,171	2,097
Ending balance		3,145	14,287
Period-end allowance allocated to:
Loans evaluated on an individual basis		0	0
Loans evaluated on a collective basis		3,145	14,287
Period-end loan balances:
Loans evaluated on an individual basis		5,556	72
Loans evaluated on a collective basis		918,334	784,029
Ending balance		923,890	784,101	687,213
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCD loans allowance for credit losses at acquisition		61
Allowance for credit losses
Beginning balance	3,352	3,352	6,893
Initial allowance on acquired PCD loans		61
Charge-offs		(186)	0
Recoveries		386	140
(Credit) provision		1,343	(1,331)
Ending balance		4,956	5,702
Period-end allowance allocated to:
Loans evaluated on an individual basis		0	0
Loans evaluated on a collective basis		4,956	5,702
Period-end loan balances:
Loans evaluated on an individual basis		6,424	5,649
Loans evaluated on a collective basis		798,902	665,931
Ending balance		805,326	671,580	542,733
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCD loans allowance for credit losses at acquisition		78
Allowance for credit losses
Beginning balance	$ 23,088	23,088	18,160
Initial allowance on acquired PCD loans		78
Charge-offs		(810)	(424)
Recoveries		366	266
(Credit) provision		10,561	795
Ending balance		33,283	18,797
Period-end allowance allocated to:
Loans evaluated on an individual basis		0	0
Loans evaluated on a collective basis		33,283	18,797
Period-end loan balances:
Loans evaluated on an individual basis		2,322	2,313
Loans evaluated on a collective basis		1,379,794	1,137,721
Ending balance		$ 1,382,116	$ 1,140,034	$ 1,158,573