Investments (Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 84,362	$ 107,159	$ 195,959	$ 215,967
Less: investment expenses	(5,743)	(5,673)	(11,888)	(11,061)
Net investment income	78,619	101,486	184,071	204,906
Fixed maturities, available-for-sale
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	54,043	66,546	129,753	130,484
Equity securities, available-for-sale
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	1	0	1	1
Trading account assets
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	445	735	1,204	1,247
Commercial mortgage and other loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	14,804	21,639	34,577	42,536
Policy loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	15,281	15,371	30,779	30,486
Short-term investments and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	462	184	1,199	459
Other long-term investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ (674)	$ 2,684	$ (1,554)	$ 10,754