Investments - Summary of Proceeds and Gains (Losses) Realized on Securities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fixed maturity securities
Proceeds received	$ 196,004	$ 442,015	$ 294,162	$ 501,739
Gross gains realized	5,506	147,774	10,285	148,316
Gross losses realized	(5,625)	(5,976)	(5,893)	(6,081)
Equity Securities, FV-NI, Realized Gain (Loss) [Abstract]
Proceeds received	10,602	1,633	12,059	17,122
Gross gains realized	1,721	389	2,040	5,134
Gross losses realized	$ (1,249)	(166)	(1,805)	(510)
Investment gain realized on transfer			$ 135,300
Reinsurance block of in-force fixed and variable annuity business		$ 2,900,000		$ 2,900,000