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	12 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Allowance for loan losses
Beginning balance	$ 39,539	$ 40,599	$ 40,599
Charge-offs	(1,550)	(3,880)
Recoveries	678	441
Provision (credit)	7,495	3,655
Provision (credit) for acquired loans	159	(5)
Ending balance	46,321	40,810	39,539
Loans individually evaluated for impairment	5,654	3,461
Loans collectively evaluated for impairment	40,440	37,023
Acquired loans evaluated for impairment	227	326
Ending balance	46,321	40,810
Loans individually evaluated for impairment	47,032	54,309
Loans collectively evaluated for impairment	4,670,155	4,225,123
Acquired nonimpaired loans	3,933,340	534,841	430,000
Acquired impaired loans	42,490	20,154	14,944
Ending balance	8,693,017	4,834,427	4,894,257
Reverse mortgage, fair value	16,200	20,000	16,500
Performing TDRs	14,995	20,200	14,953
Owner-occupied commercial
Allowance for loan losses
Beginning balance	5,057	5,422	5,422
Charge-offs	0	(10)
Recoveries	3	5
Provision (credit)	(111)	(58)
Provision (credit) for acquired loans	0	0
Ending balance	4,949	5,359	5,057
Loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	4,856	5,347
Acquired loans evaluated for impairment	93	12
Ending balance	4,949	5,359
Loans individually evaluated for impairment	5,384	4,342
Loans collectively evaluated for impairment	1,198,337	938,166
Acquired nonimpaired loans	105,154	133,007
Acquired impaired loans	4,070	5,147	4,248
Ending balance	1,312,945	1,080,662	1,059,974
Commercial mortgages
Allowance for loan losses
Beginning balance	6,806	5,891	5,891
Charge-offs	(2)	(48)
Recoveries	29	134
Provision (credit)	(156)	617
Provision (credit) for acquired loans	2	23
Ending balance	6,679	6,617	6,806
Loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	6,600	6,528
Acquired loans evaluated for impairment	79	89
Ending balance	6,679	6,617
Loans individually evaluated for impairment	3,999	5,946
Loans collectively evaluated for impairment	753,911	970,750
Acquired nonimpaired loans	1,575,527	178,518
Acquired impaired loans	19,715	9,210	7,504
Ending balance	2,353,152	1,164,424	1,162,739
Construction
Allowance for loan losses
Beginning balance	3,712	2,861	2,861
Charge-offs	0	0
Recoveries	1	1
Provision (credit)	331	27
Provision (credit) for acquired loans	0	(25)
Ending balance	4,044	2,864	3,712
Loans individually evaluated for impairment	367	0
Loans collectively evaluated for impairment	3,663	2,857
Acquired loans evaluated for impairment	14	7
Ending balance	4,044	2,864
Loans individually evaluated for impairment	2,781	6,490
Loans collectively evaluated for impairment	347,035	267,293
Acquired nonimpaired loans	225,245	15,259
Acquired impaired loans	636	901	749
Ending balance	575,697	289,943	316,566
Commercial and Industrial
Allowance for loan losses
Beginning balance	14,211	16,732	16,732
Charge-offs	(742)	(3,360)
Recoveries	358	80
Provision (credit)	7,123	2,650
Provision (credit) for acquired loans	66	0
Ending balance	21,016	16,102	14,211
Loans individually evaluated for impairment	4,588	2,632
Loans collectively evaluated for impairment	16,427	13,296
Acquired loans evaluated for impairment	1	174
Ending balance	21,016	16,102
Loans individually evaluated for impairment	16,109	16,993
Loans collectively evaluated for impairment	1,415,689	1,361,517
Acquired nonimpaired loans	782,160	107,183
Acquired impaired loans	6,130	3,870	1,531
Ending balance	2,220,088	1,489,563	1,472,489
Residential
Allowance for loan losses
Beginning balance	1,428	1,798	1,798
Charge-offs	(122)	0
Recoveries	(14)	14
Provision (credit)	51	(129)
Provision (credit) for acquired loans	58	(3)
Ending balance	1,401	1,680	1,428
Loans individually evaluated for impairment	533	643
Loans collectively evaluated for impairment	830	1,001
Acquired loans evaluated for impairment	38	35
Ending balance	1,401	1,679
Loans individually evaluated for impairment	10,590	12,861
Loans collectively evaluated for impairment	130,499	145,753
Acquired nonimpaired loans	949,804	67,722
Acquired impaired loans	8,483	777	761
Ending balance	1,099,376	227,113	201,550
Consumer
Allowance for loan losses
Beginning balance	8,325	7,895	7,895
Charge-offs	(684)	(462)
Recoveries	301	207
Provision (credit)	257	548
Provision (credit) for acquired loans	33	0
Ending balance	8,232	8,188	8,325
Loans individually evaluated for impairment	166	186
Loans collectively evaluated for impairment	8,064	7,994
Acquired loans evaluated for impairment	2	9
Ending balance	8,232	8,189
Loans individually evaluated for impairment	8,169	7,677
Loans collectively evaluated for impairment	824,684	541,644
Acquired nonimpaired loans	295,450	33,152
Acquired impaired loans	3,456	249	151
Ending balance	$ 1,131,759	$ 582,722	$ 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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- Definition

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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A valuation allowance for financing receivables that are expected to be uncollectible.

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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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