Changes in Accumulated Other Comprehensive Income by Component - Summary (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Accumulated other comprehensive income
Beginning balance	$ 480,461	$ 460,305
Other comprehensive loss before reclassifications	(1,307)	(542)
Losses reclassified from other comprehensive income	36	9
Net current period other comprehensive loss	(1,271)	(533)
Ending balance	493,102	438,179
Realized loss (less than)	100	100
Changes in other comprehensive (loss) income, tax expense (benefit)	300	100
Accumulated Other Comprehensive Income, net of taxes
Accumulated other comprehensive income
Beginning balance	5,563	2,919
Ending balance	$ 4,292	$ 2,386

Amount of realized 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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