Investments (Mortgage Loans by Maturity Date) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Mortgage Loans on Real Estate [Line Items]
Mortgage loans, gross of valuation allowances	$ 2,534,694	$ 2,496,786
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%	100.00%
Due within five years
Mortgage Loans on Real Estate [Line Items]
Mortgage loans, gross of valuation allowances	968,162	987,109
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	38.20%	39.50%
Due after five years through ten years
Mortgage Loans on Real Estate [Line Items]
Mortgage loans, gross of valuation allowances	998,196	984,289
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	39.40%	39.40%
Due after ten years
Mortgage Loans on Real Estate [Line Items]
Mortgage loans, gross of valuation allowances	$ 568,336	$ 525,388
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	22.40%	21.10%