Investments (Changes in Net Unrealized Gains/Losses on Investments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Investments [Abstract]
Fixed maturity securities available for sale carried at fair value	$ 3,347,516	$ 1,383,290	$ 485,108	$ 2,900,810
Adjustment for effect on other balance sheet accounts:
Deferred policy acquisition costs and deferred sales inducements	(1,448,951)	(704,445)	(204,198)	(1,505,346)
Deferred income tax asset/liability	(398,700)	(142,558)	(58,992)	(293,048)
Total adjustment for effect on other balance sheet accounts	(1,847,651)	(847,003)	(263,190)	(1,798,394)
Change in net unrealized gains/losses on investments carried at fair value	$ 1,499,865	$ 536,287	$ 221,918	$ 1,102,416