Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax
Other comprehensive income (loss) before reclassifications			$ 91,630	$ 60,023
Reclassification adjustments for (gains) losses included in net income (loss)			(758)	(2,501)
Total other comprehensive income, net of tax	$ 1,189	$ 4,647	90,872	57,522
(Losses) Gains on Available-For-Sale Debt Securities
AOCI Attributable to Parent, Net of Tax
Balance, beginning			40,226	(6,613)
Other comprehensive income (loss) before reclassifications			92,027	65,284
Reclassification adjustments for (gains) losses included in net income (loss)			(758)	(10,576)
Total other comprehensive income, net of tax			91,269	54,708
Balance, end	131,495	48,095	131,495	48,095
Losses on Derivatives Used for Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax
Balance, beginning			0	(2,814)
Other comprehensive income (loss) before reclassifications			(397)	(5,261)
Reclassification adjustments for (gains) losses included in net income (loss)			0	8,075
Total other comprehensive income, net of tax			(397)	2,814
Balance, end	(397)	0	(397)	0
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax
Balance, beginning			40,226	(9,427)
Balance, end	$ 131,098	$ 48,095	$ 131,098	$ 48,095