Other Comprehensive Income - Summary of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Unrealized gains arising during the period, before U.S. income taxes	$ 53,545	$ 22,928	$ 48,449	$ 44,406
U.S. income taxes	(6,937)	(1,908)	(5,559)	(3,355)
Unrealized gains arising during the period, net of U.S. income taxes	46,608	21,020	42,890	41,051
Less reclassification adjustment:
Net realized investment gains	305	331	520	103
U.S. income taxes	(10)	(43)	(24)	(44)
Reclassification adjustment for investment gains realized in net income	295	288	496	59
Other comprehensive income	$ 46,313	$ 20,732	$ 42,394	$ 40,992