Changes in Accumulated Other Comprehensive Income by Component - Summary of Changes (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	$ 399,952	$ 338,842	$ 296,456
Other comprehensive (loss) income before reclassifications	(844)	1,149	(1,005)
Losses reclassified from other comprehensive income	165	7	143
Net current period other comprehensive (loss) income	(679)	1,156	(862)
Balance	440,780	399,952	338,842
Realized (loss) gain on sales of available-for-sale securities	(200)		(200)
Changes in other comprehensive income (loss), tax expense (benefit)	(100)	300	(500)
Maximum
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Realized (loss) gain on sales of available-for-sale securities		(100)
Accumulated Other Comprehensive Income (Loss), net of Taxes
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	837	(319)	543
Balance	$ 158	$ 837	$ (319)

Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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