Changes in Accumulated Other Comprehensive Income by Component - Summary (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated other comprehensive income
Beginning balance	$ 449,648	$ 408,134	$ 440,780	$ 399,952
Other comprehensive income (loss) before reclassifications			2,754	(1,694)
(Gains) losses reclassified from other comprehensive income			(90)	145
Net current period other comprehensive income (loss)			2,664	(1,549)
Ending balance	455,299	419,580	455,299	419,580
Changes in other comprehensive (loss) income, tax expense (benefit)			700	(300)
Accumulated Other Comprehensive Income, net of taxes
Accumulated other comprehensive income
Beginning balance	2,365	(204)	158	837
Ending balance	$ 2,822	$ (712)	$ 2,822	$ (712)

Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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