Net Investment Gains (Losses) (Net Investment Gains (Losses)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Fixed maturity securities, gains	$ 8,240	$ 4,931
Fixed maturity securities, losses	(2,071)	(4,847)
Net realized gains on investment sales	8,572	0
Change in unrealized losses	(24,335)	(154,467)
Investment funds	47,671	30,183
Real estate	12,909	(687)
Other	773	(18,398)
Net realized and unrealized gains (losses) on investments in earnings before allowance for expected credit losses	51,759	(143,285)
Fixed maturity securities	(18,159)	(31,750)
Loans receivable	1,239	(2,139)
Change in allowance for expected credit losses on investments	(16,920)	(33,889)
Net investment gains (losses)	34,839	(177,174)
Income tax (expense) benefit	(5,887)	37,207
After-tax net investment gains (losses)	$ 28,952	$ (139,967)