Allowance for Loan Losses - Summary of Changes in Loan Allowance (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of changes in allowance for loan losses
Balance at the beginning of the year				$ 32,086				$ 31,083	$ 32,086	$ 31,083	$ 29,746
Charge-offs									(3,605)	(4,838)	(6,085)
Recoveries of loans previously charged-off									1,432	1,621	2,491
Provision for loan losses	$ 1,162	$ 1,065	$ 1,750	$ 1,152	$ 1,338	$ 884	$ 1,131	$ 867	5,129	4,220	4,931
Balance at the end of the year	$ 35,042				$ 32,086				$ 35,042	$ 32,086	$ 31,083