Loans and Allowance for Loan Losses - Disaggregated analysis of activity in the allowance for acquired credit impaired loans (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Nov. 30, 2017
Allowance for loan losses:
Provision (benefit) for loan losses	$ 12,777	$ 13,783	$ 11,890
Reduction due to loan removals	(723)	(1,134)	(821)
Non-acquired loans
Allowance for loan losses:
Provision (benefit) for loan losses	9,283	10,763	8,684
Loans individually evaluated for impairment	1,346	1,628	1,624
Loans collectively evaluated for impairment	55,581	49,566	41,824
Loans:
Loans individually evaluated for impairment	58,532	57,018	63,423
Loans collectively evaluated for impairment	9,194,299	7,876,268	6,428,732
Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	4,604	4,627	3,395
Provision (benefit) for loan losses	1,183	1,111	2,053
Reduction due to loan removals	(723)	(1,134)	(821)
Balance at the end of the period	5,064	4,604	4,627
Loans collectively evaluated for impairment	5,064	4,604	4,627
Loans:
Loans collectively evaluated for impairment	361,846	489,723	623,430
Carrying value	361,846	489,723	623,430	$ 78,967
Acquired non-credit impaired loans
Allowance for loan losses:
Provision (benefit) for loan losses	2,311	1,909	1,153
Loans:
Loans collectively evaluated for impairment	1,760,427	2,594,826	3,507,907
Carrying value	1,760,427	2,594,826
Residential real estate
Loans:
Carrying value	163,359	207,482
Residential real estate \| Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	2,246	3,553	2,419
Provision (benefit) for loan losses	716	(892)	1,662
Reduction due to loan removals	(407)	(415)	(528)
Balance at the end of the period	2,555	2,246	3,553
Loans collectively evaluated for impairment	2,555	2,246	3,553
Loans:
Loans collectively evaluated for impairment	163,359	207,482	260,787
Carrying value	163,359	207,482	260,787
Commercial non-owner occupied real estate \| Construction and land development \| Non-acquired loans
Allowance for loan losses:
Loans individually evaluated for impairment	617	788	1,063
Loans collectively evaluated for impairment	5,487	4,894	4,858
Loans:
Loans individually evaluated for impairment	35,201	37,913	43,230
Loans collectively evaluated for impairment	933,159	803,532	787,645
Commercial non-owner occupied real estate \| Construction and land development \| Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	717	180	139
Provision (benefit) for loan losses	(148)	657	163
Reduction due to loan removals		(120)	(122)
Balance at the end of the period	569	717	180
Loans collectively evaluated for impairment	569	717	180
Loans:
Loans collectively evaluated for impairment	25,032	32,942	49,649
Carrying value	25,032	32,942	49,649
Commercial non-owner occupied real estate \| Construction and land development \| Acquired non-credit impaired loans
Loans:
Carrying value	33,569	165,070
Commercial non-owner occupied real estate \| Other commercial non-owner occupied real estate \| Non-acquired loans
Allowance for loan losses:
Loans individually evaluated for impairment		70	125
Loans collectively evaluated for impairment	10,699	8,684	6,400
Loans:
Loans individually evaluated for impairment	379	1,025	1,375
Loans collectively evaluated for impairment	1,810,759	1,414,526	1,007,518
Commercial non-owner occupied real estate \| Other commercial non-owner occupied real estate \| Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	801	288	41
Provision (benefit) for loan losses	577	532	247
Reduction due to loan removals	(1)	(19)
Balance at the end of the period	1,377	801	288
Loans collectively evaluated for impairment	1,377	801	288
Loans:
Loans collectively evaluated for impairment	130,938	196,764	234,595
Carrying value	130,938	196,764	234,595
Commercial non-owner occupied real estate \| Other commercial non-owner occupied real estate \| Acquired non-credit impaired loans
Loans:
Loans collectively evaluated for impairment	447,441	679,253	817,166
Carrying value	447,441	679,253
Consumer loans \| Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	761	461	558
Provision (benefit) for loan losses	(222)	303	(83)
Reduction due to loan removals		(3)	(14)
Balance at the end of the period	539	761	461
Loans collectively evaluated for impairment	539	761	461
Loans:
Loans collectively evaluated for impairment	35,488	42,492	51,453
Carrying value	35,488	42,492	51,453
Consumer loans \| Acquired non-credit impaired loans
Loans:
Carrying value	774,647	983,015
Consumer loans \| Home equity loans \| Non-acquired loans
Allowance for loan losses:
Loans individually evaluated for impairment	132	142	135
Loans collectively evaluated for impairment	3,056	3,292	3,115
Loans:
Loans individually evaluated for impairment	2,461	2,826	3,011
Loans collectively evaluated for impairment	516,167	492,322	434,631
Consumer loans \| Home equity loans \| Acquired non-credit impaired loans
Loans:
Loans collectively evaluated for impairment	188,732	242,425	320,591
Carrying value	188,732	242,425
Commercial and industrial
Loans:
Carrying value	7,029	10,043
Commercial and industrial \| Non-acquired loans
Allowance for loan losses:
Loans individually evaluated for impairment	366	416	15
Loans collectively evaluated for impairment	7,973	7,038	5,473
Loans:
Loans individually evaluated for impairment	6,578	1,291	1,156
Loans collectively evaluated for impairment	1,274,281	1,053,661	814,031
Commercial and industrial \| Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	79	145	238
Provision (benefit) for loan losses	260	511	64
Reduction due to loan removals	(315)	(577)	(157)
Balance at the end of the period	24	79	145
Loans collectively evaluated for impairment	24	79	145
Loans:
Loans collectively evaluated for impairment	7,029	10,043	26,946
Carrying value	7,029	10,043	26,946
Commercial and industrial \| Acquired non-credit impaired loans
Loans:
Loans collectively evaluated for impairment	101,880	212,537	398,696
Carrying value	101,880	212,537
Other income producing property \| Non-acquired loans
Allowance for loan losses:
Loans individually evaluated for impairment	50	142	178
Loans collectively evaluated for impairment	1,286	1,304	1,197
Loans:
Loans individually evaluated for impairment	2,024	2,872	3,138
Loans collectively evaluated for impairment	216,593	211,481	190,709
Other income producing property \| Acquired non-credit impaired loans
Loans:
Loans collectively evaluated for impairment	95,697	133,110	196,669
Carrying value	95,697	133,110
Consumer
Loans:
Carrying value	35,488	42,492
Consumer \| Non-acquired loans
Allowance for loan losses:
Loans individually evaluated for impairment	55	2	7
Loans collectively evaluated for impairment	3,892	3,099	2,781
Loans:
Loans individually evaluated for impairment	173	188	239
Loans collectively evaluated for impairment	538,308	448,476	378,746
Consumer \| Acquired credit impaired loans
Loans:
Carrying value	35,488	42,492
Consumer \| Acquired non-credit impaired loans
Loans:
Loans collectively evaluated for impairment	89,484	111,777	137,710
Carrying value	89,484	111,777
Commercial loans \| Acquired non-credit impaired loans
Loans:
Carrying value	985,780	1,611,811
Commercial loans \| Construction and land development \| Acquired non-credit impaired loans
Loans:
Loans collectively evaluated for impairment	33,569	165,070	403,357
Commercial loans \| Other commercial non-owner occupied real estate \| Acquired non-credit impaired loans
Loans:
Loans collectively evaluated for impairment	$ 307,193	$ 421,841	$ 521,818

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The sum of the periodic provision charged to earnings before adjustment for amounts covered under loss sharing agreement.

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No definition available.

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Reserve for loans impairments recorded after acquisition as a result of current information and events which result in it being probable that estimated cash flows will be less than previously expected or because actual cash flows are less than cash flows previously expected. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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The undiscounted sum of all amounts, including amounts deemed principal, interest, fees, penalties, and other under the loan, owed to the investor at the reporting date, whether or not currently due and whether or not any such amounts have been written or charged off by the investor. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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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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Amount of increase (decrease) in allowance for credit loss on financing receivable.

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

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