Investments (Realized Investment Gains Losses Net) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	$ (116,749)	$ (167,278)	$ (80,186)
Fixed Maturities
Schedule of Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	46,738	(13,340)	27,123
Equity securities
Schedule of Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	0	0	(125)
Commercial mortgage and other loans
Schedule of Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	297	(271)	(337)
LPs/LLCs
Schedule of Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	(3,400)	849	(221)
Derivatives
Schedule of Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	(160,368)	(154,208)	(106,625)
Short-term investments and cash equivalents
Schedule of Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	$ (16)	$ (308)	$ (1)