Investments (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity security sold suring the year		$ 1,000,000
Loans originated during the year		21,500,000	37,300,000
Recognized valuation losses		650,000	609,000	400,000
Specific principle balances requiring a valuation allowance		0	7,000,000	7,000,000
Mortgage loans, write-downs		600,000
Interest recorded for impaired loans		0	300,000	100,000
Equity securities realized gains	2,700,000
Number of loans outstanding more than 180 days		1
Principal balance of loan outstanding for more than six months		0	7,000,000
Real estate investments		41,439,000	34,472,000
Realized gains (losses) on investments		13,200,000	6,063,000	5,475,000
Securities transfered from available-to-sale to held-to-maturity category		5,000,000	0
Unrealized holding loss at the date of transfer		227,000	41,000	14,000
Debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Realized gains (losses) on investments		14,500,000	6,200,000	6,200,000
Held-to-maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Sold Security, Realized Gain (Loss)		300,000
Real Estate [Member]
Schedule of Available-for-sale Securities [Line Items]
Real estate investments		18,800,000	19,200,000
Operating income recognized on real estate investment properties		1,600,000	1,600,000	1,600,000
Realized gains (losses) on investments		2,600,000	(100,000)	(100,000)
Below Investment Grade Debt Security [Member] | Debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt securities below investment grade		165,800,000	146,200,000
Debt securities below investment grade, percentage of total invested assets		1.80%	1.70%
Other-than Temporary Impairment Write-down on Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Realized gains (losses) on investments		$ 1,200,000