Fair Value of Financial Instruments Fair value measurement (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Jan. 23, 2004
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities	$ 71,010,000	$ 79,534,000
Available-for-sale Securities, Debt Securities	71,010,000	79,534,000
Equity investments, at fair value (cost of $2,024 and $2,305, respectively)	3,304,000	3,548,000
Other Investments	2,000,000	2,000,000
Short-term investments, at cost which approximates fair value	586,000	585,000
Investments	78,376,000	88,000,000
Assets	370,248,000	372,800,000
Debt Instrument, Face Amount	14,903,000	13,655,000
Senior unsecured debentures	25,888,000	23,730,000	125,000,000
Subordinated debt	28,781,000	23,774,000
Long-term Debt	69,572,000	61,159,000
Equity Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Equity investments, at fair value (cost of $2,024 and $2,305, respectively)	3,304,000	3,548,000
US Government Agencies Debt Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities	22,645,000	24,915,000
Foreign Government Debt Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities	4,029,000	3,782,000
Fair Value, Inputs, Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Financial Instruments, Owned, Corporate Debt, at Fair Value	0	0
Mortgage-backed Securities Available-for-sale, Fair Value Disclosure	0	0
Financial Instruments, Owned, Mortgages, Mortgage-backed and Asset-backed Securities, at Fair Value	0	0
Municipal Debt Securities, at Carrying Value	0	0
Financial Instruments, Owned, Other Sovereign Government Obligations, at Fair Value	0	0
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	0	0
Equity investments, at fair value (cost of $2,024 and $2,305, respectively)	3,304,000
Other Investments	0	0
Short-term investments, at cost which approximates fair value	0	0
Assets	3,304,000	3,548,000
Senior unsecured debentures	0	0
Subordinated debt	0	0
Long-term Debt	14,903,000	13,655,000
Fair Value, Inputs, Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities, Debt Securities	71,010,000	79,534,000
Financial Instruments, Owned, Corporate Debt, at Fair Value	36,205,000	37,357,000
Mortgage-backed Securities Available-for-sale, Fair Value Disclosure	651,000	5,043,000
Financial Instruments, Owned, Mortgages, Mortgage-backed and Asset-backed Securities, at Fair Value	160,000	1,092,000
Municipal Debt Securities, at Carrying Value	7,320,000	7,345,000
Financial Instruments, Owned, Other Sovereign Government Obligations, at Fair Value	4,029,000	3,782,000
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	22,645,000	24,915,000
Equity investments, at fair value (cost of $2,024 and $2,305, respectively)	0	0
Assets	73,596,000	82,119,000
Debt Instrument, Face Amount	0	0
Long-term Debt	54,669,000	47,504,000
Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Financial Instruments, Owned, Corporate Debt, at Fair Value	0	0
Mortgage-backed Securities Available-for-sale, Fair Value Disclosure	0	0
Financial Instruments, Owned, Mortgages, Mortgage-backed and Asset-backed Securities, at Fair Value	0	0
Municipal Debt Securities, at Carrying Value	0	0
Financial Instruments, Owned, Other Sovereign Government Obligations, at Fair Value	0	0
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	0	0
Equity investments, at fair value (cost of $2,024 and $2,305, respectively)	0	0
Other Investments	0	0
Short-term investments, at cost which approximates fair value	0	0
Assets	0	0
Debt Instrument, Face Amount	0	0
Senior unsecured debentures	0	0
Subordinated debt	0	0
Long-term Debt	0	0
Summary of Investments, by Type [Domain]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments	76,900,000	85,667,000
Debt, State Government [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities	7,320,000	7,345,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities	651,000	5,043,000
Asset-backed Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities	160,000	1,092,000
Corporate Debt Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale Securities	36,205,000	37,357,000
Other Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other Investments	2,000,000	2,000,000
Short-term Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Short-term investments, at cost which approximates fair value	586,000	585,000
Debt Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Debt Instrument, Face Amount	14,903,000	13,655,000
Senior Notes [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Senior unsecured debentures	25,888,000	23,730,000
Subordinated Debt [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Subordinated debt	28,781,000	23,774,000
Liability [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Long-term Debt	$ 69,572,000	$ 61,159,000