Loans and Allowance for Loan Losses - Table of loan payment estimates - (Details) - USD ($) $ in Thousands	Jan. 03, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Contractual principal and interest		$ 741,268		$ 778,822	$ 822,340
Non-accretable difference		(26,160)		(17,502)	(22,222)
Cash flows expected to be collected		715,108		761,320	800,118
Accretable Yield		(132,575)		(155,379)	(164,098)
Carrying value		582,533		605,941	636,020
Allowance for loan losses on acquired loans		(3,670)	$ (3,741)	(3,395)	(3,403)	$ (3,752)	$ (3,706)
Acquired credit impaired loans | SBFC
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Contractual principal and interest	$ 73,365
Non-accretable difference	(12,912)
Cash flows expected to be collected	60,453
Accretable difference	(4,603)
Carrying value	55,850
Impaired non-acquired and acquired loans accounted under FASB ASC topic 310-20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Contractual principal and interest	1,010,000
Carrying value	991,500
Fair value adjustment	$ 18,800
Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		1,455,555		836,699	885,657
Residential real estate | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		249,666		258,100	268,968
Allowance for loan losses on acquired loans		(2,776)	(2,741)	(2,419)	(2,492)	(2,592)	(2,986)
Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		276,590		44,718	46,458
Commercial owner occupied real estate loan | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		207,572		27,195	29,444
Consumer real estate | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		53,302		59,300	61,866
Allowance for loan losses on acquired loans		(462)	(548)		(544)	(778)
Consumer real estate | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		656,906		569,149	603,890
Commercial and industrial | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		25,796		25,347	26,658
Allowance for loan losses on acquired loans		(243)	(320)	(238)	(182)	(196)	(174)
Commercial and industrial | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		101,427		13,641	14,201
Other income producing property | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		76,924		39,342	43,152
Consumer | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		53,302		59,300	61,866
Allowance for loan losses on acquired loans		(462)		(558)	(543)		(313)
Consumer | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		136,136		142,654	148,512
Commercial | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Allowance for loan losses on acquired loans				(41)	(41)		(56)
Commercial | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		662,513		124,896	133,255
Commercial loans 1000000 or more | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		8,439		8,617	10,958
Construction and land development | Commercial non-owner occupied real estate | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		46,248		44,373	47,081
Allowance for loan losses on acquired loans		(189)	(92)		(145)	(151)
Construction and land development | Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		76,886		10,090	10,683
Construction and land development | Commercial | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Allowance for loan losses on acquired loans		(189)		(139)	(145)		$ (177)
Other commercial non-owner occupied real estate | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value				210,204
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		199,082		210,204	220,489
Allowance for loan losses on acquired loans			$ (40)		(40)	$ (35)
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		199,704		34,628	35,775
Home equity loans | Consumer real estate | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		164,291		160,879	168,758
Consumer | Consumer real estate | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		136,136		142,654	148,512
Other Consumer | Consumer real estate | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		793,042		711,803	752,402
Consumer Owner Occupied Loans | Consumer real estate | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Carrying value		$ 492,615		$ 408,270	$ 435,132