Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to Parent, Net of Tax
Balance, beginning	$ 143,090
Total other comprehensive (loss) income, net of tax	(63,170)	$ 59,498
Balance, end	79,920
Gains (Losses) on Available-For-Sale Debt Securities
AOCI Attributable to Parent, Net of Tax
Balance, beginning	143,443	40,226
Other comprehensive income before reclassifications	(63,370)	60,142
Reclassification adjustments for gains included in net income	(243)	(644)
Total other comprehensive (loss) income, net of tax	(63,613)	59,498
Balance, end	79,830	99,724
(Losses) Gains on Derivatives Used for Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax
Balance, beginning	(353)	0
Other comprehensive income before reclassifications	443	0
Reclassification adjustments for gains included in net income	0	0
Total other comprehensive (loss) income, net of tax	443	0
Balance, end	90	0
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax
Balance, beginning	143,090	40,226
Other comprehensive income before reclassifications	(62,927)	60,142
Reclassification adjustments for gains included in net income	(243)	(644)
Total other comprehensive (loss) income, net of tax	(63,170)	59,498
Balance, end	$ 79,920	$ 99,724