Investments (Mortgage Loans by Real Estate Geographic Location) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Mortgage Loans On Real Estate Geographic Location Of Property [Line Items]
Recorded investment	$ 2,534,694	$ 2,496,786
Percentage of total	100.00%	100.00%
Pacific
Mortgage Loans On Real Estate Geographic Location Of Property [Line Items]
Recorded investment	678,578	671,822
Percentage of total	26.80%	26.90%
South Atlantic
Mortgage Loans On Real Estate Geographic Location Of Property [Line Items]
Recorded investment	521,853	543,658
Percentage of total	20.60%	21.80%
Mountain
Mortgage Loans On Real Estate Geographic Location Of Property [Line Items]
Recorded investment	374,874	334,446
Percentage of total	14.80%	13.40%
Middle Atlantic
Mortgage Loans On Real Estate Geographic Location Of Property [Line Items]
Recorded investment	251,235	266,802
Percentage of total	10.00%	10.70%
West North Central
Mortgage Loans On Real Estate Geographic Location Of Property [Line Items]
Recorded investment	160,561	138,442
Percentage of total	6.30%	5.50%
East North Central
Mortgage Loans On Real Estate Geographic Location Of Property [Line Items]
Recorded investment	243,936	236,766
Percentage of total	9.60%	9.50%
West South Central
Mortgage Loans On Real Estate Geographic Location Of Property [Line Items]
Recorded investment	167,894	168,246
Percentage of total	6.60%	6.70%
East South Central
Mortgage Loans On Real Estate Geographic Location Of Property [Line Items]
Recorded investment	59,384	59,625
Percentage of total	2.30%	2.40%
New England
Mortgage Loans On Real Estate Geographic Location Of Property [Line Items]
Recorded investment	$ 76,379	$ 76,979
Percentage of total	3.00%	3.10%