Changes in Accumulated Other Comprehensive Income by Component - Summary (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated other comprehensive income
Beginning balance	$ 442,549	$ 394,344	$ 440,780	$ 399,952
Other comprehensive income (loss) before reclassifications			2,286	(1,167)
(Gains) losses reclassified from other comprehensive income			(79)	126
Net current period other comprehensive income (loss)			2,207	(1,041)
Ending balance	449,648	408,134	449,648	408,134
Changes in other comprehensive (loss) income, tax expense			(600)	300
Accumulated Other Comprehensive Income, net of taxes
Accumulated other comprehensive income
Beginning balance	1,574	(301)	158	837
Ending balance	$ 2,365	$ (204)	$ 2,365	$ (204)

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

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