ALLOWANCE FOR LOAN AND LEASE LOSSES AND CREDIT QUALITY INFORMATION - Schedule of Allowance for Loan Losses and Loan Balances (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Allowance for loan losses
Beginning balance	$ 45,364	$ 41,037	$ 39,539	$ 40,599	$ 40,599
Charge-offs	(2,496)	(3,803)	(18,374)	(10,646)
Recoveries	682	862	2,536	1,995
Provision (credit)	3,980	3,834	23,126	9,940
Provision (credit) for acquired loans	141	(118)	844	(76)
Ending balance	47,671	41,812	47,671	41,812	39,539
Loans individually evaluated for impairment	4,348	5,164	4,348	5,164
Loans collectively evaluated for impairment	43,148	36,419	43,148	36,419
Acquired loans individually evaluated for impairment	175	229	175	229
Ending balance	47,671	41,812	47,671	41,812
Loans individually evaluated for impairment	52,256	51,879	52,256	51,879
Loans collectively evaluated for impairment	5,013,755	4,384,467	5,013,755	4,384,467
Acquired nonimpaired loans	3,421,089	465,438	3,421,089	465,438	430,000
Acquired impaired loans			31,815	17,493	14,944
Ending balance	8,518,915	4,919,277	8,518,915	4,919,277	4,894,257
Reverse mortgage, fair value	17,700	16,600	17,700	16,600	16,500
Performing TDRs			14,125	15,200	14,953
Owner-occupied commercial
Allowance for loan losses
Beginning balance	4,480	5,284	5,057	5,422	5,422
Charge-offs	(12)	0	(20)	(351)
Recoveries	4	16	85	28
Provision (credit)	23	273	(614)	419
Provision (credit) for acquired loans	9	0	(4)	55
Ending balance	4,504	5,573	4,504	5,573	5,057
Loans individually evaluated for impairment	156	9	156	9
Loans collectively evaluated for impairment	4,269	5,546	4,269	5,546
Acquired loans individually evaluated for impairment	79	18	79	18
Ending balance	4,504	5,573	4,504	5,573
Loans individually evaluated for impairment	9,263	2,829	9,263	2,829
Loans collectively evaluated for impairment	935,306	958,356	935,306	958,356
Acquired nonimpaired loans	322,030	119,403	322,030	119,403
Acquired impaired loans			6,809	4,816	4,248
Ending balance	1,273,408	1,085,404	1,273,408	1,085,404	1,059,974
Commercial mortgages
Allowance for loan losses
Beginning balance	6,544	6,951	6,806	5,891	5,891
Charge-offs	2	0	(153)	(48)
Recoveries	120	52	547	189
Provision (credit)	97	(598)	(533)	356
Provision (credit) for acquired loans	(26)	(21)	70	(4)
Ending balance	6,737	6,384	6,737	6,384	6,806
Loans individually evaluated for impairment	0	0	0	0
Loans collectively evaluated for impairment	6,690	6,300	6,690	6,300
Acquired loans individually evaluated for impairment	47	84	47	84
Ending balance	6,737	6,384	6,737	6,384
Loans individually evaluated for impairment	2,325	6,502	2,325	6,502
Loans collectively evaluated for impairment	1,019,723	961,345	1,019,723	961,345
Acquired nonimpaired loans	1,237,282	156,483	1,237,282	156,483
Acquired impaired loans			12,655	8,951	7,504
Ending balance	2,271,985	1,133,281	2,271,985	1,133,281	1,162,739
Construction
Allowance for loan losses
Beginning balance	2,984	3,289	3,712	2,861	2,861
Charge-offs	0	(1,475)	(42)	(1,475)
Recoveries	2	1	4	3
Provision (credit)	(105)	1,657	(787)	2,106
Provision (credit) for acquired loans	0	0	(6)	(23)
Ending balance	2,881	3,472	2,881	3,472	3,712
Loans individually evaluated for impairment	0	444	0	444
Loans collectively evaluated for impairment	2,873	3,019	2,873	3,019
Acquired loans individually evaluated for impairment	8	9	8	9
Ending balance	2,881	3,472	2,881	3,472
Loans individually evaluated for impairment	0	2,903	0	2,903
Loans collectively evaluated for impairment	375,664	322,822	375,664	322,822
Acquired nonimpaired loans	138,251	7,025	138,251	7,025
Acquired impaired loans			487	737	749
Ending balance	514,402	333,487	514,402	333,487	316,566
Commercial and Industrial
Allowance for loan losses
Beginning balance	22,004	15,842	14,211	16,732	16,732
Charge-offs	(1,441)	(1,761)	(15,185)	(6,861)
Recoveries	297	621	858	1,060
Provision (credit)	3,595	1,947	24,286	5,730
Provision (credit) for acquired loans	49	(82)	334	(94)
Ending balance	24,504	16,567	24,504	16,567	14,211
Loans individually evaluated for impairment	3,534	3,970	3,534	3,970
Loans collectively evaluated for impairment	20,969	12,517	20,969	12,517
Acquired loans individually evaluated for impairment	1	80	1	80
Ending balance	24,504	16,567	24,504	16,567
Loans individually evaluated for impairment	21,135	19,910	21,135	19,910
Loans collectively evaluated for impairment	1,657,748	1,387,143	1,657,748	1,387,143
Acquired nonimpaired loans	605,804	97,552	605,804	97,552
Acquired impaired loans			1,664	2,070	1,531
Ending balance	2,286,351	1,506,675	2,286,351	1,506,675	1,472,489
Residential
Allowance for loan losses
Beginning balance	1,358	1,519	1,428	1,798	1,798
Charge-offs	(3)	0	(288)	(54)
Recoveries	(60)	28	(76)	117
Provision (credit)	43	(71)	118	(382)
Provision (credit) for acquired loans	(8)	(1)	148	(4)
Ending balance	1,330	1,475	1,330	1,475	1,428
Loans individually evaluated for impairment	478	570	478	570
Loans collectively evaluated for impairment	813	870	813	870
Acquired loans individually evaluated for impairment	39	35	39	35
Ending balance	1,330	1,475	1,330	1,475
Loans individually evaluated for impairment	12,031	11,479	12,031	11,479
Loans collectively evaluated for impairment	138,121	134,074	138,121	134,074
Acquired nonimpaired loans	876,089	60,407	876,089	60,407
Acquired impaired loans			7,655	766	761
Ending balance	1,033,896	206,726	1,033,896	206,726	201,550
Consumer
Allowance for loan losses
Beginning balance	7,994	8,152	8,325	7,895	7,895
Charge-offs	(1,042)	(567)	(2,686)	(1,857)
Recoveries	319	144	1,118	598
Provision (credit)	327	626	656	1,711
Provision (credit) for acquired loans	117	(14)	302	(6)
Ending balance	7,715	8,341	7,715	8,341	8,325
Loans individually evaluated for impairment	180	171	180	171
Loans collectively evaluated for impairment	7,534	8,167	7,534	8,167
Acquired loans individually evaluated for impairment	1	3	1	3
Ending balance	7,715	8,341	7,715	8,341
Loans individually evaluated for impairment	7,502	8,256	7,502	8,256
Loans collectively evaluated for impairment	887,193	620,727	887,193	620,727
Acquired nonimpaired loans	241,633	24,568	241,633	24,568
Acquired impaired loans			2,545	153	151
Ending balance	$ 1,138,873	$ 653,704	$ 1,138,873	$ 653,704	$ 680,939

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of addition to allowance reserve for credit loss arising from purchase of loan and lease portfolios.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Allowance for credit losses acquired and evaluated for impairment.

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Loans and leases receivable acquired non impaired loans.

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Loans And Leases Receivable Troubled Debt Restructurings Recorded Investment Accrual Status

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Provision for loan and lease losses loans acquired.

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Provisions credit for loan and lease losses.

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Reverse Mortgage, Fair Value

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