Investments (Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 88,077	$ 110,017	$ 172,353	$ 207,724
Less: investment expenses	(4,615)	(4,455)	(9,310)	(8,912)
Net investment income	83,462	105,562	163,043	198,812
Equity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	103	221	205	442
Commercial mortgage and other loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	12,322	13,435	26,098	25,926
Policy loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	17,615	16,766	34,926	32,965
Other invested assets
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	2,165	18,060	(1,744)	27,971
Short-term investments and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	580	1,839	2,612	4,150
Available-for-sale | Fixed maturities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	54,897	59,370	109,463	115,636
Trading | Fixed maturities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 395	$ 326	$ 793	$ 634