Investments (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	$ 511,725,000		$ 511,725,000		$ 497,545,000
Cost or Amortized Cost	465,583,000		465,583,000		456,634,000
Gross Unrealized Gains	50,616,000		50,616,000		45,449,000
Gross Unrealized Losses	(4,474,000)		(4,474,000)		(4,538,000)
Net Unrealized Gains (losses)	46,142,000		46,142,000		40,911,000
Applicable federal income taxes			(16,150,000)		(14,319,000)
Net unrealized gains - net of tax			29,992,000		26,592,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Number of Securities, total	282		282		289
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair value, total	127,500,000		127,500,000		106,933,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross unrealized loss, total	(4,474,000)		(4,474,000)		(4,538,000)
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
One year or less, Fair Value	129,753		129,753
Excess of one year to five years, Fair Value	211,721		211,721
Excess of five years to ten years, Fair Value	22,174		22,174
Excess of ten years, Fair Value	3,155		3,155
Total maturities, Fair Value	366,803		366,803
Asset-backed securities	43,845		43,845
Available-for-sale Securities, Debt Securities, Current	410,648		410,648
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
One year or less, Amortized Cost Basis	129,659		129,659
Excess of one year to five years, Amortized Cost Basis	210,120		210,120
Excess of five years to ten years, Amortized Cost Basis	22,204		22,204
Excess of ten years, Amortized Cost Basis	3,036		3,036
Total maturities, Amortized Cost Basis	365,019		365,019
Asset-backed securities	43,765		43,765
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Total	408,784		408,784
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Limited partnerships - net gain (loss)	(4,883,000)	(3,637,000)	537,000	(5,177,000)
Total net losses	(5,453,000)	(1,963,000)	(73,000)	(3,432,000)
Available For Sale Securities Gain Loss Activity [Abstract]
Realized net gains (losses) on the disposal of securities	(109,000)	1,636,000	(205,000)	2,044,000
Mark-to-market adjustment	(369,000)	156,000	(313,000)	(645,000)
Equity in (losses) of limited partnership investments - realized and unrealized	(4,883,000)	(3,637,000)	537,000	(5,177,000)
Write-downs based upon objective criteria	(345,000)	(118,000)	(345,000)	(118,000)
Recovery of prior write-downs upon sale or disposal	253,000	0	253,000	464,000
Gain (Loss) on Investments	(5,453,000)	(1,963,000)	(73,000)	(3,432,000)
Net unrealized gain (loss) on investments	1,670,000		3,861,000
Unrealized losses in limited partnership			306,000
Undistributed earnings of limited partnership, net of taxes	15,877,000		15,877,000
U.S. government obligations [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	69,433,000		69,433,000		73,137,000
Cost or Amortized Cost	69,433,000		69,433,000		73,009,000
Gross Unrealized Gains	52,000		52,000		139,000
Gross Unrealized Losses	(52,000)		(52,000)		(11,000)
Net Unrealized Gains (losses)	0		0		128,000
Government sponsored entities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value					349,000
Cost or Amortized Cost					345,000
Gross Unrealized Gains					4,000
Gross Unrealized Losses					0
Net Unrealized Gains (losses)					4,000
Residential mortgage-backed securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	18,165,000		18,165,000		21,872,000
Cost or Amortized Cost	18,347,000		18,347,000		21,778,000
Gross Unrealized Gains	533,000		533,000		619,000
Gross Unrealized Losses	(715,000)		(715,000)		(525,000)
Net Unrealized Gains (losses)	(182,000)		(182,000)		94,000
Commercial mortgage-backed securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	15,153,000		15,153,000		11,300,000
Cost or Amortized Cost	14,821,000		14,821,000		11,388,000
Gross Unrealized Gains	490,000		490,000		116,000
Gross Unrealized Losses	(158,000)		(158,000)		(204,000)
Net Unrealized Gains (losses)	332,000		332,000		(88,000)
States and municipal obligations [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	174,216,000		174,216,000		190,035,000
Cost or Amortized Cost	173,165,000		173,165,000		188,991,000
Gross Unrealized Gains	1,092,000		1,092,000		1,275,000
Gross Unrealized Losses	(41,000)		(41,000)		(231,000)
Net Unrealized Gains (losses)	1,051,000		1,051,000		1,044,000
Corporate securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	112,182,000		112,182,000		91,646,000
Cost or Amortized Cost	111,368,000		111,368,000		91,949,000
Gross Unrealized Gains	1,844,000		1,844,000		1,429,000
Gross Unrealized Losses	(1,030,000)		(1,030,000)		(1,732,000)
Net Unrealized Gains (losses)	814,000		814,000		(303,000)
Foreign government obligations [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	21,499,000		21,499,000		21,121,000
Cost or Amortized Cost	21,650,000		21,650,000		21,483,000
Gross Unrealized Gains	161,000		161,000		168,000
Gross Unrealized Losses	(312,000)		(312,000)		(530,000)
Net Unrealized Gains (losses)	(151,000)		(151,000)		(362,000)
Total fixed maturities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	410,648,000		410,648,000		409,460,000
Cost or Amortized Cost	408,784,000		408,784,000		408,943,000
Gross Unrealized Gains	4,172,000		4,172,000		3,750,000
Gross Unrealized Losses	(2,308,000)		(2,308,000)		(3,233,000)
Net Unrealized Gains (losses)	1,864,000		1,864,000		517,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Number of Securities Less than 12 months	204		204		206
Number of Securities More than 12 months	35		35		44
Number of Securities, total	239		239		250
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair value, 12 months or less	98,248,000		98,248,000		86,470,000
Fair value, 12 months or longer	14,548,000		14,548,000		11,930,000
Fair value, total	112,796,000		112,796,000		98,400,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross unrealized loss, less than 12 months	(1,978,000)		(1,978,000)		(2,303,000)
Gross unrealized loss, 12 months or longer	(330,000)		(330,000)		(930,000)
Gross unrealized loss, total	(2,308,000)		(2,308,000)		(3,233,000)
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Gross gains	792,000	1,161,000	1,342,000	2,158,000
Gross losses	(1,181,000)	(402,000)	(2,152,000)	(1,869,000)
Net gains (losses)	(389,000)	759,000	(810,000)	289,000
Financial institutions [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	10,121,000		10,121,000		9,428,000
Cost or Amortized Cost	5,012,000		5,012,000		4,955,000
Gross Unrealized Gains	5,260,000		5,260,000		4,778,000
Gross Unrealized Losses	(151,000)		(151,000)		(305,000)
Net Unrealized Gains (losses)	5,109,000		5,109,000		4,473,000
Industrial & Miscellaneous [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	90,956,000		90,956,000		78,657,000
Cost or Amortized Cost	51,787,000		51,787,000		42,736,000
Gross Unrealized Gains	41,184,000		41,184,000		36,921,000
Gross Unrealized Losses	(2,015,000)		(2,015,000)		(1,000,000)
Net Unrealized Gains (losses)	39,169,000		39,169,000		35,921,000
Total equity securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	101,077,000		101,077,000		88,085,000
Cost or Amortized Cost	56,799,000		56,799,000		47,691,000
Gross Unrealized Gains	46,444,000		46,444,000		41,699,000
Gross Unrealized Losses	(2,166,000)		(2,166,000)		(1,305,000)
Net Unrealized Gains (losses)	44,278,000		44,278,000		40,394,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Number of Securities Less than 12 months	33		33		35
Number of Securities More than 12 months	10		10		4
Number of Securities, total	43		43		39
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair value, 12 months or less	11,244,000		11,244,000		8,317,000
Fair value, 12 months or longer	3,460,000		3,460,000		216,000
Fair value, total	14,704,000		14,704,000		8,533,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross unrealized loss, less than 12 months	(1,785,000)		(1,785,000)		(1,275,000)
Gross unrealized loss, 12 months or longer	(381,000)		(381,000)		(30,000)
Gross unrealized loss, total	(2,166,000)		(2,166,000)		(1,305,000)
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Gross gains	152,000	1,198,000	675,000	2,229,000
Gross losses	(333,000)	(283,000)	(475,000)	(773,000)
Net gains (losses)	$ (181,000)	$ 915,000	$ 200,000	$ 1,456,000