Fair Value (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Carrying Value [Member]
Assets [Abstract]
Limited partnerships	$ 53,280	$ 54,705
Liabilities [Abstract]
Short-term borrowings	10,000	10,000
Fair Value [Member]
Assets [Abstract]
Limited partnerships	53,280	54,705
Liabilities [Abstract]
Short-term borrowings	10,000	10,000
Insurance Linked Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Sales	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning of period balance	17,050	17,242
Total gain or losses (realized or unrealized) included in earnings (or changes in net assets)	(165)	387
Purchases	400	6,522
Settlements	(3,644)	(7,101)
End of period balance	13,641	17,050
Insurance Linked Securities [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Percentage of variance in values of securities (in hundredths)	3.00%
Insurance Linked Securities [Member] | Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Percentage of variance in values of securities (in hundredths)	0.00%
Level 1 [Member]
Assets [Abstract]
Limited partnerships	0
Liabilities [Abstract]
Short-term borrowings	0
Level 2 [Member]
Assets [Abstract]
Limited partnerships	0
Liabilities [Abstract]
Short-term borrowings	10,000
Level 3 [Member]
Assets [Abstract]
Limited partnerships	53,280
Liabilities [Abstract]
Short-term borrowings	0
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
US government obligations	69,433	73,137
Government sponsored entities	0	349
Residential mortgage-backed securities	18,165	21,872
Commercial mortgage-backed securities	15,153	11,300
State and municipal obligations	174,216	190,035
Corporate securities	110,802	90,141
Options embedded in convertible securities	1,380	1,505
Foreign government obligations	21,499	21,121
Total fixed maturities	410,648	409,460
Equity securities	101,077	88,085
Short term	3,346	3,675
Cash equivalents	85,098	81,756
Total fair value	600,169	582,976
Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
US government obligations	69,433	73,137
Government sponsored entities	0	0
Residential mortgage-backed securities	0	0
Commercial mortgage-backed securities	0	0
State and municipal obligations	0
Corporate securities	0	0
Options embedded in convertible securities		0
Foreign government obligations	0	0
Total fixed maturities	69,433	73,137
Equity securities	101,077	88,085
Short term	3,225	2,982
Cash equivalents	0	0
Total fair value	173,735	164,204
Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
US government obligations	0	0
Government sponsored entities	0	349
Residential mortgage-backed securities	18,165	21,872
Commercial mortgage-backed securities	15,153	11,300
State and municipal obligations	174,216	190,035
Corporate securities	97,161	73,091
Options embedded in convertible securities	1,380	1,505
Foreign government obligations	21,499	21,121
Total fixed maturities	327,574	319,273
Equity securities	0	0
Short term	121	693
Cash equivalents	85,098	81,756
Total fair value	412,793	401,722
Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
US government obligations	0	0
Government sponsored entities	0	0
Residential mortgage-backed securities	0	0
Commercial mortgage-backed securities	0	0
State and municipal obligations	0
Corporate securities	13,641	17,050
Options embedded in convertible securities		0
Foreign government obligations	0	0
Total fixed maturities	13,641	17,050
Equity securities	0	0
Cash equivalents	0	0
Total fair value	$ 13,641	$ 17,050