Investments (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of net investment income
Investments income	$ 31,621	$ 32,807	$ 33,418
Less investment expenses	1,423	1,469	1,280
Net investment income	30,198	31,338	32,138
Fixed maturity securities [Member]
Summary of net investment income
Investments income	31,348	32,454	32,524
Common stock [Member]
Summary of net investment income
Investments income			626
Preferred stock [Member]
Summary of net investment income
Investments income	230	185	201
Short-term investments and cash and cash equivalents [Member]
Summary of net investment income
Investments income	$ 43	$ 168	$ 67