Investments (Mortgage Loans by Credit Quality Indicator) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Credit Quality Indicators [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 3,136,764	$ 2,718,709
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%	100.00%
High Investment Grade [Member]
Credit Quality Indicators [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 1,621,601	$ 1,326,199
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	51.70%	48.80%
Investment Grade [Member]
Credit Quality Indicators [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 1,397,996	$ 1,235,046
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	44.60%	45.40%
Average [Member]
Credit Quality Indicators [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 87,196	$ 118,152
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	2.80%	4.40%
Watch List [Member]
Credit Quality Indicators [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 13,550	$ 22,285
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	0.40%	0.80%
In Or Near Default [Member]
Credit Quality Indicators [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 16,421	$ 17,027
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	0.50%	0.60%