Investments (Fair Value Below Amortized Cost of Gross Unrealized Losses for Fixed Maturity and Equity Securities) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 386,530	$ 627,451
% of Total	100.00%	100.00%
Less than 20%
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 275,128	$ 463,109
% of Total	71.20%	73.80%
20% or more for less than six months
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 69,739	$ 142,495
% of Total	18.00%	22.70%
20% or more for six months or greater
Gross unrealized losses with number of securities [Line Items]
Gross Unrealized Losses	$ 41,663	$ 21,847
% of Total	10.80%	3.50%