Investments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013 Security Agreement	Jun. 30, 2012	Jun. 30, 2013 Security Agreement	Jun. 30, 2012	Dec. 31, 2012 Security
Schedule of Available-For-Sale Securities [Line Items]
Applicable federal income taxes	$ (18,327)				$ (19,098)
Net unrealized gains - net of tax	34,038				35,467
Available-for-sale securities continuous unrealized loss position [Abstract]
Number of Securities, total	563		563		259
Available-for-sale securities continuous unrealized loss position, Fair Value [Abstract]
Fair value, total	181,021		181,021		123,485
Available-for-sale securities continuous unrealized loss position, aggregate losses [Abstract]
Gross unrealized loss, total	(5,978)		(5,978)		(2,937)
Available-for-sale securities debt maturities fair value [Abstract]
One year or less, Fair Value	95,838		95,838
Excess of one year to five years, Fair Value	186,069		186,069
Excess of five years to ten years, Fair Value	28,815		28,815
Excess of ten years, Fair Value	2,803		2,803
Contractual maturities, Fair Value	313,525		313,525
Asset-backed securities, Fair Value	65,578		65,578
Available-for-sale securities, Fair Value	379,103		379,103
Available-for-sale securities debt maturities amortized cost basis [Abstract]
One year or less, Amortized Cost Basis	95,614		95,614
Excess of one year to five years, Amortized Cost Basis	187,129		187,129
Excess of five years to ten years, Amortized Cost Basis	29,173		29,173
Excess of ten years, Amortized Cost Basis	2,561		2,561
Contractual maturities, Amortized Cost Basis	314,477		314,477
Asset-backed securities, Amortized Cost Basis	64,984		64,984
Available-for-sale securities debt maturities amortized cost basis, Total	379,461		379,461
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Limited partnerships - net gain (loss)	(1,275)	(4,883)	2,438	537
Totals	719	(5,453)	15,066	(73)
Available for sale securities gain loss activity [Abstract]
Realized net gains (losses) on the disposal of securities	1,554	(109)	10,798	(205)
Mark-to-market adjustment	195	(369)	405	(313)
Equity in gains (losses) of limited partnership investments - realized and unrealized	(1,275)	(4,883)	2,438	537
Write-downs based upon objective criteria	(68)	(345)	(74)	(345)
Recovery of prior write-downs upon sale or disposal	313	253	1,499	253
Net realized gains (losses) on investments	719	(5,453)	15,066	(73)
Net unrealized gain (loss) on investments	(2,980)		(247)
Net unrealized gains in limited partnership			4,193
Undistributed earnings of limited partnership, net of taxes	21,049		21,049
Committed funds for bridge loans	21,600		21,600
Number of bridge loan agreements	2		2
U.S. government obligations [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	68,021		68,021		70,742
Cost or Amortized Cost	68,049		68,049		70,720
Gross Unrealized Gains	21		21		43
Gross Unrealized Losses	(49)		(49)		(21)
Net Unrealized Gains (Losses)	(28)		(28)		22
Residential mortgage-backed securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	16,535		16,535		25,040
Cost or Amortized Cost	15,367		15,367		23,954
Gross Unrealized Gains	1,376		1,376		1,218
Gross Unrealized Losses	(208)		(208)		(132)
Net Unrealized Gains (Losses)	1,168		1,168		1,086
Commercial mortgage-backed securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	25,391		25,391		11,828
Cost or Amortized Cost	25,706		25,706		11,006
Gross Unrealized Gains	156		156		849
Gross Unrealized Losses	(471)		(471)		(27)
Net Unrealized Gains (Losses)	(315)		(315)		822
States and municipal obligations [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	113,251		113,251		194,865
Cost or Amortized Cost	113,368		113,368		194,258
Gross Unrealized Gains	269		269		757
Gross Unrealized Losses	(386)		(386)		(150)
Net Unrealized Gains (Losses)	(117)		(117)		607
Corporate securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	133,963		133,963		120,596
Cost or Amortized Cost	134,637		134,637		118,574
Gross Unrealized Gains	2,043		2,043		2,923
Gross Unrealized Losses	(2,717)		(2,717)		(901)
Net Unrealized Gains (Losses)	(674)		(674)		2,022
Foreign government obligations [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	21,942		21,942		22,598
Cost or Amortized Cost	22,334		22,334		22,047
Gross Unrealized Gains	86		86		602
Gross Unrealized Losses	(478)		(478)		(51)
Net Unrealized Gains (Losses)	(392)		(392)		551
Total fixed maturities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	379,103		379,103		445,669
Cost or Amortized Cost	379,461		379,461		440,559
Gross Unrealized Gains	3,951		3,951		6,392
Gross Unrealized Losses	(4,309)		(4,309)		(1,282)
Net Unrealized Gains (Losses)	(358)		(358)		5,110
Available-for-sale securities continuous unrealized loss position [Abstract]
Number of Securities Less than 12 months	489		489		170
Number of Securities More than 12 months	47		47		58
Number of Securities, total	536		536		228
Available-for-sale securities continuous unrealized loss position, Fair Value [Abstract]
Fair value, 12 months or less	151,419		151,419		90,607
Fair value, 12 months or longer	19,545		19,545		19,283
Fair value, total	170,964		170,964		109,890
Available-for-sale securities continuous unrealized loss position, aggregate losses [Abstract]
Gross unrealized loss, less than 12 months	(3,655)		(3,655)		(483)
Gross unrealized loss, 12 months or longer	(654)		(654)		(799)
Gross unrealized loss, total	(4,309)		(4,309)		(1,282)
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Gross gains	2,233	792	3,652	1,342
Gross losses	(883)	(1,181)	(2,220)	(2,152)
Net realized gains (losses)	1,350	(389)	1,432	(810)
Financial institutions [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	13,664		13,664		12,394
Cost or Amortized Cost	5,638		5,638		5,925
Gross Unrealized Gains	8,028		8,028		6,542
Gross Unrealized Losses	(2)		(2)		(73)
Net Unrealized Gains (Losses)	8,026		8,026		6,469
Industrial & Miscellaneous [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	107,282		107,282		95,188
Cost or Amortized Cost	62,585		62,585		52,202
Gross Unrealized Gains	46,364		46,364		44,568
Gross Unrealized Losses	(1,667)		(1,667)		(1,582)
Net Unrealized Gains (Losses)	44,697		44,697		42,986
Total equity securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	120,946		120,946		107,582
Cost or Amortized Cost	68,223		68,223		58,127
Gross Unrealized Gains	54,392		54,392		51,110
Gross Unrealized Losses	(1,669)		(1,669)		(1,655)
Net Unrealized Gains (Losses)	52,723		52,723		49,455
Available-for-sale securities continuous unrealized loss position [Abstract]
Number of Securities Less than 12 months	23		23		20
Number of Securities More than 12 months	4		4		11
Number of Securities, total	27		27		31
Available-for-sale securities continuous unrealized loss position, Fair Value [Abstract]
Fair value, 12 months or less	7,516		7,516		6,955
Fair value, 12 months or longer	2,541		2,541		6,640
Fair value, total	10,057		10,057		13,595
Available-for-sale securities continuous unrealized loss position, aggregate losses [Abstract]
Gross unrealized loss, less than 12 months	(1,272)		(1,272)		(842)
Gross unrealized loss, 12 months or longer	(397)		(397)		(813)
Gross unrealized loss, total	(1,669)		(1,669)		(1,655)
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Gross gains	893	152	12,605	675
Gross losses	(249)	(333)	(1,409)	(475)
Net realized gains (losses)	644	(181)	11,196	200
Total available-for-sale securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Fair Value	500,049		500,049		553,251
Cost or Amortized Cost	447,684		447,684		498,686
Gross Unrealized Gains	58,343		58,343		57,502
Gross Unrealized Losses	(5,978)		(5,978)		(2,937)
Net Unrealized Gains (Losses)	$ 52,365		$ 52,365		$ 54,565