Other Comprehensive (Loss) Income - Summary of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Unrealized (losses) gains arising during the period, before U.S. income taxes	$ (5,096)	$ 21,478
U.S. income taxes	1,378	(1,447)
Unrealized (losses) gains arising during the period, net of U.S. income taxes	(3,718)	20,031
Less reclassification adjustment:
Net realized investment gains (losses)	214	(228)
U.S. income taxes	(13)	(1)
Reclassification adjustment for investment gains (losses) realized in net income	201	(229)
Other comprehensive (loss) income	$ (3,919)	$ 20,260

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