Other Comprehensive Income (Loss) - Summary of Components of Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Unrealized gains (losses) arising during the period, before U.S. income taxes	$ 51,381	$ (23,201)	$ 11,091
U.S. income taxes	(3,510)	483	(2,374)
Unrealized gains (losses) arising during the period, net of U.S. income taxes	47,871	(22,718)	8,717
Less reclassification adjustment:
Net realized investment gains (losses)	1,081	(554)	(835)
U.S. income taxes	(152)	39	333
Reclassification adjustment for investment gains (losses) realized in net income	929	(515)	(502)
Other comprehensive income (loss)	$ 46,942	$ (22,203)	$ 9,219