Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	$ 144,896	$ 198,923
Derivatives designated as cash flow hedges
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	13,357	4,839
Fixed maturities
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	129,479	191,339
Fixed maturities | Securities Related to Other Than Temporary Impairments
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	15	1
Equity securities, available-for-sale
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	3	3
Affiliated notes
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	1,877	2,351
Other investments
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	$ 165	$ 390