Changes in Accumulated Other Comprehensive Income by Component - Reclassification Adjustments (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax (expense) benefit	$ (5,498)		$ (7,311)		$ (13,797)	$ (13,903)
Net income	9,565	$ 24,653	23,101	$ 20,190	34,218	43,291
Realized Gains (Losses) on Sale of Available-for-sale Securities | Amounts Reclassified from Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains (losses) from the sale of available-for-sale securities	276		(76)		228	(87)
Tax (expense) benefit	(77)		19		(65)	21
Net income	$ 199		$ (57)		$ 163	$ (66)