Investments (Commercial Mortgage and Other Loans) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Commercial mortgage loans	$ 1,608,389		$ 1,562,632
Commercial mortgage loans, Percentage	93.40%	93.20%
Valuation allowance	(4,003)		(4,154)
Total net commercial and agricultural mortgage loans by property type	1,718,172		1,673,143
Total commercial mortgage and other loans	1,726,582		1,681,553
Total Commercial Mortgage By Propterty Type	1,722,175		1,677,297
Other Loans and Leases Receivable	8,410		8,410
Other Loans Valuation Allowance	0		0
Uncollateralized Loans [Member]
Other Loans and Leases Receivable	8,410		8,410
Office buildings [Member]
Commercial mortgage loans	254,707		244,072
Commercial mortgage loans, Percentage	14.80%	14.60%
Retail stores [Member]
Commercial mortgage loans	452,984		439,679
Commercial mortgage loans, Percentage	26.30%	26.20%
Apartment Complexes [Member]
Commercial mortgage loans	418,703		401,568
Commercial mortgage loans, Percentage	24.30%	23.90%
Industrial Buildings [Member]
Commercial mortgage loans	291,662		286,104
Commercial mortgage loans, Percentage	16.90%	17.10%
Agricultural Properties [Member]
Commercial mortgage loans	113,786		114,665
Commercial mortgage loans, Percentage	6.60%	6.80%
Hospitality [Member]
Commercial mortgage loans	91,560		92,126
Commercial mortgage loans, Percentage	5.30%	5.50%
Other [Member]
Commercial mortgage loans	$ 98,773		$ 99,083
Commercial mortgage loans, Percentage	5.80%	5.90%
California [Member]
Commercial mortgage loans, Percentage	21.00%
New Jersey [Member]
Commercial mortgage loans, Percentage	9.00%
Texas [Member]
Commercial mortgage loans, Percentage	11.00%