Loans and Allowance for Loan Losses - Changes in Accretable Yield on Purchase Credit Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accounts Notes And Loans Receivable [Line Items]
Purchased Credit Impaired Accretable yield, Accretion			$ 5,745	$ 3,545
Purchased Credit Impaired
Accounts Notes And Loans Receivable [Line Items]
Purchased Credit Impaired Accretable yield, Beginning balance	$ (20,169)	$ (1,845)	(17,682)	(2,444)
Purchased Credit Impaired Accretable yield, Additions through the acquisition of the Clayton Banks		(18,457)		(18,457)
Purchased Credit Impaired Accretable yield, Principal reductions/ pay-offs	(84)	(690)	(3,536)	(1,680)
Purchased Credit Impaired Accretable yield, Recoveries				(23)
Purchased Credit Impaired Accretable yield, Accretion	2,103	1,646	6,943	3,258
Purchased Credit Impaired Accretable yield, Other changes	6		(3,869)
Purchased Credit Impaired Accretable yield, Ending balance	$ (18,144)	$ (19,346)	$ (18,144)	$ (19,346)