Investments Allowance for Expected Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Marketable Securities
Balance	$ 2,510
Credit losses on securities with no previously recorded credit losses	(39)	$ 2,471
Net increases (decreases) in allowance on previously impaired securities	(39)
Balance	2,471	2,471
Corporate and other securities
Marketable Securities
Balance	2,510
Credit losses on securities with no previously recorded credit losses		2,471
Net increases (decreases) in allowance on previously impaired securities	(39)
Balance	$ 2,471	$ 2,471