Investments (Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 108,564	$ 108,029	$ 304,523	$ 323,996
Less: investment expenses	(4,821)	(5,814)	(16,709)	(16,875)
Fixed maturities, available-for-sale
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	56,901	68,428	186,654	198,912
Equity securities, available-for-sale
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	0	0	1	1
Trading account assets
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	424	774	1,628	2,021
Commercial mortgage and other loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	11,792	21,891	46,369	64,427
Policy loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	16,034	16,155	46,813	46,641
Short-term investments and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	351	203	1,550	662
Other long-term investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 23,062	$ 578	$ 21,508	$ 11,332