Investments (Details 5) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Major categories of the Company's net investment income
Total gross investment income									$ 28,102	$ 27,540	$ 27,461
Investment expenses									(1,084)	(1,200)	(1,219)
Net investment income	6,698	6,801	6,605	6,914	6,702	6,495	6,597	6,546	27,018	26,340	26,242
Fixed Maturity Securities Available for Sale [Member]
Major categories of the Company's net investment income
Total gross investment income									27,167	26,769	26,571
Short-term Investments [Member]
Major categories of the Company's net investment income
Total gross investment income									489	590	819
Equity Securities [Member]
Major categories of the Company's net investment income
Total gross investment income									$ 446	$ 181	$ 71