Investments (Realized Investment Gains Losses, Net) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	$ (1,547)	$ 39,584	$ 8,117	$ (61,301)
Fixed maturities
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	(88)	27,418	(6,826)	20,745
Commercial mortgage and other loans
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	(82)	54	(314)	160
Other invested assets
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	14	0	(296)	12
Derivatives
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	(1,395)	12,129	15,709	(82,194)
Short-term investments and cash equivalents
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	$ 4	$ (17)	$ (156)	$ (24)