Loans and Allowance for Loan Losses - Changes in Accretable Yield on Purchase Credit Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Purchased Credit Impaired Accretable yield, Accretion	$ 1,687	$ 1,160
Purchased Credit Impaired
Accounts Notes And Loans Receivable [Line Items]
Purchased Credit Impaired Accretable yield, Beginning balance	(17,682)	(2,444)
Purchased Credit Impaired Accretable yield, Principal reductions/ pay-offs	(1,294)	(698)
Purchased Credit Impaired Accretable yield, Recoveries		(23)
Purchased Credit Impaired Accretable yield, Accretion	2,201	1,023
Purchased Credit Impaired Accretable yield, Other changes	(180)
Purchased Credit Impaired Accretable yield, Ending balance	$ (16,955)	$ (2,142)