Loans and Allowance for Loan Losses - Disaggregated analysis of activity in the allowance for acquired credit impaired loans (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Allowance for loan losses:
Provision for loan losses before benefit attributable to FDIC loss share agreements		$ 912	$ 8,082	$ 6,175
Total provision for loan losses charged to operations	$ 2,062	912	8,082	6,198
Provision for loan losses recorded through the FDIC loss share receivable				(23)
Reduction due to loan removals	(198)	(326)	(544)	(675)
Non-acquired loans
Allowance for loan losses:
Provision for loan losses before benefit attributable to FDIC loss share agreements		775	6,512	5,255
Total provision for loan losses charged to operations	1,939	775	6,512	5,255
Loans individually evaluated for impairment	1,862	1,379	1,862	1,379
Loans collectively evaluated for impairment	39,679	35,940	39,679	35,940
Loans:
Loans individually evaluated for impairment	60,792	21,187	60,792	21,187
Loans collectively evaluated for impairment	6,169,535	4,986,926	6,169,535	4,986,926
Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	3,741	3,752	3,395	3,706
Provision for loan losses before benefit attributable to FDIC loss share agreements	127	(23)	819	372
Benefits attributable to FDIC loss share agreements				23
Total provision for loan losses charged to operations	127	(23)	819	395
Provision for loan losses recorded through the FDIC loss share receivable				(23)
Reduction due to loan removals	(198)	(326)	(544)	(675)
Balance at the end of the period	3,670	3,403	3,670	3,403
Loans collectively evaluated for impairment	3,670	3,403	3,670	3,403
Loans:
Loans collectively evaluated for impairment	582,533	636,020	582,533	636,020
Carrying value	582,533	636,020	582,533	636,020	$ 605,941
Other commercial non-owner occupied real estate \| Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations			1,129	964
Other commercial non-owner occupied real estate \| Acquired credit impaired loans
Loans:
Carrying value					210,204
Residential real estate \| Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	2,741	2,592	2,419	2,986
Provision for loan losses before benefit attributable to FDIC loss share agreements	184	2	743	(178)
Benefits attributable to FDIC loss share agreements				23
Total provision for loan losses charged to operations	184	2	743	(155)
Provision for loan losses recorded through the FDIC loss share receivable				(23)
Reduction due to loan removals	(149)	(102)	(386)	(316)
Balance at the end of the period	2,776	2,492	2,776	2,492
Loans collectively evaluated for impairment	2,776	2,492	2,776	2,492
Loans:
Loans collectively evaluated for impairment	249,666	268,968	249,666	268,968
Carrying value	249,666	268,968	249,666	268,968	258,100
Commercial non-owner occupied real estate \| Construction and land development \| Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations	(88)	(795)
Loans individually evaluated for impairment	1,266	359	1,266	359
Loans collectively evaluated for impairment	4,706	3,752	4,706	3,752
Loans:
Loans individually evaluated for impairment	42,638	3,431	42,638	3,431
Loans collectively evaluated for impairment	724,319	558,905	724,319	558,905
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	92	151
Provision for loan losses before benefit attributable to FDIC loss share agreements	133
Total provision for loan losses charged to operations	133
Reduction due to loan removals	(36)	(6)
Balance at the end of the period	189	145	189	145
Loans collectively evaluated for impairment	189	145	189	145
Loans:
Loans collectively evaluated for impairment	46,248	47,081	46,248	47,081
Carrying value	46,248	47,081	46,248	47,081	44,373
Commercial non-owner occupied real estate \| Other commercial non-owner occupied real estate \| Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations	(7)	(93)
Loans individually evaluated for impairment	133	181	133	181
Loans collectively evaluated for impairment	6,104	4,410	6,104	4,410
Loans:
Loans individually evaluated for impairment	716	764	716	764
Loans collectively evaluated for impairment	949,154	629,673	949,154	629,673
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	40	35
Provision for loan losses before benefit attributable to FDIC loss share agreements	(40)
Total provision for loan losses charged to operations	(40)
Reduction due to loan removals		5
Balance at the end of the period		40		40
Loans collectively evaluated for impairment		40		40
Loans:
Loans collectively evaluated for impairment	199,082	220,489	199,082	220,489
Carrying value	199,082	220,489	199,082	220,489	210,204
Consumer real estate \| Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	548	778
Provision for loan losses before benefit attributable to FDIC loss share agreements	(85)	(23)
Total provision for loan losses charged to operations	(85)	(23)
Reduction due to loan removals	(1)	(211)
Balance at the end of the period	462	544	462	544
Loans collectively evaluated for impairment	462	544	462	544
Loans:
Loans collectively evaluated for impairment	53,302	61,866	53,302	61,866
Carrying value	53,302	61,866	53,302	61,866	59,300
Consumer real estate \| Home equity loans \| Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations	(171)	69
Loans individually evaluated for impairment	116	38	116	38
Loans collectively evaluated for impairment	2,981	3,243	2,981	3,243
Loans:
Loans individually evaluated for impairment	2,623	1,599	2,623	1,599
Loans collectively evaluated for impairment	417,137	362,226	417,137	362,226
Commercial and industrial \| Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations	469	368	726	887
Loans individually evaluated for impairment	18	385	18	385
Loans collectively evaluated for impairment	5,185	4,325	5,185	4,325
Loans:
Loans individually evaluated for impairment	627	1,453	627	1,453
Loans collectively evaluated for impairment	781,130	616,072	781,130	616,072
Commercial and industrial \| Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	320	196	238	174
Provision for loan losses before benefit attributable to FDIC loss share agreements	(65)	(2)	71	38
Total provision for loan losses charged to operations	(65)	(2)	71	38
Reduction due to loan removals	(12)	(12)	(66)	(30)
Balance at the end of the period	243	182	243	182
Loans collectively evaluated for impairment	243	182	243	182
Loans:
Loans collectively evaluated for impairment	25,796	26,658	25,796	26,658
Carrying value	25,796	26,658	25,796	26,658	25,347
Other income producing property \| Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations	(10)	(201)	(214)	(384)
Loans individually evaluated for impairment	211	289	211	289
Loans collectively evaluated for impairment	1,177	1,330	1,177	1,330
Loans:
Loans individually evaluated for impairment	3,605	4,319	3,605	4,319
Loans collectively evaluated for impairment	190,730	175,276	190,730	175,276
Consumer \| Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations	889	1,094
Loans individually evaluated for impairment	7	4	7	4
Loans collectively evaluated for impairment	2,685	2,304	2,685	2,304
Loans:
Loans individually evaluated for impairment	254	142	254	142
Loans collectively evaluated for impairment	371,504	305,545	371,504	305,545
Consumer \| Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period			558	313
Provision for loan losses before benefit attributable to FDIC loss share agreements			(85)	511
Total provision for loan losses charged to operations			(85)	511
Reduction due to loan removals			(11)	(281)
Balance at the end of the period	462	543	462	543
Loans:
Carrying value	53,302	61,866	53,302	61,866	59,300
Consumer \| Home equity loans \| Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations			(6)	880
Commercial loans 1000000 or more \| Acquired credit impaired loans
Loans:
Loans collectively evaluated for impairment	8,439	10,958	8,439	10,958
Carrying value	8,439	10,958	8,439	10,958	$ 8,617
Commercial \| Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period			41	56
Provision for loan losses before benefit attributable to FDIC loss share agreements			(40)	1
Total provision for loan losses charged to operations			(40)	1
Reduction due to loan removals			(1)	(16)
Balance at the end of the period		41		41
Commercial \| Construction and land development \| Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations			1,819	(694)
Commercial \| Construction and land development \| Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period			139	177
Provision for loan losses before benefit attributable to FDIC loss share agreements			130
Total provision for loan losses charged to operations			130
Reduction due to loan removals			(80)	(32)
Balance at the end of the period	$ 189	$ 145	$ 189	$ 145

Amount represents the benefits adjustment attributable to FDIC loss share agreements.

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Provision for loan losses recorded through the FDIC loss share receivable - Amount of reduction in the reserve for loans impairments as a result of current information and events which result in it being probable that estimated cash flows will be significantly higher than previously expected or because actual cash flows are significantly greater than cash flows previously expected for 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 sum of the periodic provision charged to earnings before adjustment for amounts covered under loss sharing agreement.

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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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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The increase (decrease) in the allowance for credit losses related to financing receivables.

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

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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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