Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Gross unrealized losses of the Company's investment portfolio
Less than 12 months, Fair Value	$ 113,208	$ 73,355
12 months or longer, Fair Value	308	3,810
Total, Fair Value	113,516	77,165
Temporarily impaired securities, Less than 12 months, Fair Value	114,371	74,912
Temporarily impaired securities, 12 months or longer, Fair Value	4,388	8,520
Temporarily impaired securities, Fair Value	118,759	83,432
Less than 12 months, Unrealized Losses	(1,318)	(642)
12 months or longer, Unrealized Losses	(17)	(174)
Total, Unrealized Losses	(1,335)	(816)
Temporarily impaired securities, Less than 12 months, Unrealized Losses	(1,334)	(658)
Temporarily impaired securities, 12 months or longer, Unrealized Losses	(890)	(417)
Temporarily impaired securities, Unrealized Losses	(2,224)	(1,075)
U.S. Treasury securities and other government corporations and agencies [Member]
Gross unrealized losses of the Company's investment portfolio
Less than 12 months, Fair Value	5,426	4,985
12 months or longer, Fair Value
Total, Fair Value	5,426	4,985
Less than 12 months, Unrealized Losses	(18)	(11)
12 months or longer, Unrealized Losses
Total, Unrealized Losses	(18)	(11)
States of the U.S. and political subdivisions of the states [Member]
Gross unrealized losses of the Company's investment portfolio
Less than 12 months, Fair Value
12 months or longer, Fair Value
Total, Fair Value
Less than 12 months, Unrealized Losses
12 months or longer, Unrealized Losses
Total, Unrealized Losses
Corporate securities [Member]
Gross unrealized losses of the Company's investment portfolio
Less than 12 months, Fair Value	24,527	24,489
12 months or longer, Fair Value
Total, Fair Value	24,527	24,489
Less than 12 months, Unrealized Losses	(267)	(85)
12 months or longer, Unrealized Losses
Total, Unrealized Losses	(267)	(85)
Mortgage-backed securities [Member]
Gross unrealized losses of the Company's investment portfolio
Less than 12 months, Fair Value	57,730	36,345
12 months or longer, Fair Value	257	3,751
Total, Fair Value	57,987	40,096
Less than 12 months, Unrealized Losses	(685)	(336)
12 months or longer, Unrealized Losses	(2)	(165)
Total, Unrealized Losses	(687)	(501)
Commercial mortgage-backed securities [Member]
Gross unrealized losses of the Company's investment portfolio
Less than 12 months, Fair Value	12,275
12 months or longer, Fair Value
Total, Fair Value	12,275
Less than 12 months, Unrealized Losses	(113)
12 months or longer, Unrealized Losses
Total, Unrealized Losses	(113)
Asset-backed securities [Member]
Gross unrealized losses of the Company's investment portfolio
Less than 12 months, Fair Value	13,250	7,536
12 months or longer, Fair Value	51	59
Total, Fair Value	13,301	7,595
Less than 12 months, Unrealized Losses	(235)	(210)
12 months or longer, Unrealized Losses	(15)	(9)
Total, Unrealized Losses	(250)	(219)
Common stock [Member]
Gross unrealized losses of the Company's investment portfolio
Temporarily impaired securities, Less than 12 months, Fair Value	1,163	1,067
Temporarily impaired securities, 12 months or longer, Fair Value	3,573	4,206
Temporarily impaired securities, Fair Value	4,736	5,273
Temporarily impaired securities, Less than 12 months, Unrealized Losses	(16)	(14)
Temporarily impaired securities, 12 months or longer, Unrealized Losses	(853)	(220)
Temporarily impaired securities, Unrealized Losses	(869)	(234)
Preferred stock [Member]
Gross unrealized losses of the Company's investment portfolio
Temporarily impaired securities, Less than 12 months, Fair Value		490
Temporarily impaired securities, 12 months or longer, Fair Value	507	504
Temporarily impaired securities, Fair Value	507	994
Temporarily impaired securities, Less than 12 months, Unrealized Losses		(2)
Temporarily impaired securities, 12 months or longer, Unrealized Losses	(20)	(23)
Temporarily impaired securities, Unrealized Losses	$ (20)	$ (25)