Investments (Realized Investment Gains Losses Net) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Gain (Loss) on Investments [Line Items]
Realized investment (gains) losses, net	$ 9,485	$ (14,242)
Fixed maturities
Gain (Loss) on Investments [Line Items]
Realized investment (gains) losses, net	(3,013)	(2,146)
Commercial mortgage and other loans
Gain (Loss) on Investments [Line Items]
Realized investment (gains) losses, net	11	(6)
Other long-term investments
Gain (Loss) on Investments [Line Items]
Realized investment (gains) losses, net	(23)	(480)
Derivatives
Gain (Loss) on Investments [Line Items]
Realized investment (gains) losses, net	12,481	(11,610)
Short-term investments
Gain (Loss) on Investments [Line Items]
Realized investment (gains) losses, net	$ 29	$ 0