Investments (Realized Investment Gains Losses, Net) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	$ (80,231)	$ (52,250)	$ 9,664	$ (100,885)
Fixed maturities
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	(4,063)	(2,489)	(6,738)	(6,673)
Commercial mortgage and other loans
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	(44)	99	(232)	106
Other invested assets
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	5	0	(310)	12
Derivatives
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	(76,353)	(49,846)	17,104	(94,323)
Short-term investments and cash equivalents
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	$ 224	$ (14)	$ (160)	$ (7)