Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investment [Line Items]
Net unrealized gains (losses) on investments	$ 107,460	$ 198,923	$ 185,050
Derivatives designated as cash flow hedges
Investment [Line Items]
Net unrealized gains (losses) on investments	14,847	4,839	(3,653)
Fixed maturities
Investment [Line Items]
Net unrealized gains (losses) on investments	90,637	191,339	184,891
Fixed maturities | Securities Related to Other Than Temporary Impairments
Investment [Line Items]
Net unrealized gains (losses) on investments	9	1	323
Equity securities, available-for-sale
Investment [Line Items]
Net unrealized gains (losses) on investments	3	3	2
Affiliated notes
Investment [Line Items]
Net unrealized gains (losses) on investments	1,660	2,351	3,113
Other investments
Investment [Line Items]
Net unrealized gains (losses) on investments	$ 304	$ 390	$ 374