Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 15,913	$ (18,449)	$ (14,132)	$ (9,129)	$ 9,487
Unrealized gain (loss) on available-for-sale securities:
Unrealized gain (loss) arising during the period	16,831	40,002	(994)	14,585	10,602
Reclassification adjustment for (gain) loss included in net income (loss)	0	(1,419)	3,575	(1,419)	3,428
Total change in unrealized gain (loss) on available-for-sale securities	16,831	38,583	3,097	13,166	14,546
Total other comprehensive income	16,831	38,583	3,097	13,166	14,546
Comprehensive income (loss)	$ 32,744	$ 20,134	$ (11,035)	$ 4,037	$ 24,033