Investments - Net Investment Gains (Losses) By Transaction Type (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Credit impairment write-downs	$ 0	$ (1,105)	$ 0
Change in intent write-downs	(5,283)	(275)	(1,530)
Net other-than-temporary impairment losses on securities recognized in net income	(5,283)	(1,380)	(1,530)
Sales and other, net	14,968	151,495	3,491
Change in fair value - equity securities	(167)	7,308	(18,323)
Change in fair value and gains realized on settlements - derivatives	(11,807)	(4,083)	3,819
Total	$ (2,289)	$ 153,340	$ (12,543)