Investments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014 Security Agreement	Sep. 30, 2013	Sep. 30, 2014 Security Agreement	Sep. 30, 2013	Dec. 31, 2013 Security
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Cost or amortized cost	$ 431,167		$ 431,167
Available-for-sale Securities, Fair Value to Amortized Cost Basis [Abstract]
Applicable federal income taxes	(29,508)				(26,432)
Net unrealized gains - net of tax	54,799				49,089
Available-for-sale securities continuous unrealized loss position [Abstract]
Number of Securities, total	519		519		516
Available-for-sale securities continuous unrealized loss position, Fair Value [Abstract]
Fair value, total	146,326		146,326		145,056
Available-for-sale securities continuous unrealized loss position, aggregate losses [Abstract]
Gross unrealized loss, total			(4,692)		(4,584)
Available-for-sale securities debt maturities fair value [Abstract]
One year or less, Fair Value	145,547		145,547
Excess of one year to five years, Fair Value	154,266		154,266
Excess of five years to ten years, Fair Value	46,520		46,520
Excess of ten years, Fair Value	8,987		8,987
Contractual maturities, Fair Value	355,320		355,320
Asset-backed securities, Fair Value	76,481		76,481
Total, Fair Value	431,801		431,801
Available-for-sale securities debt maturities amortized cost basis [Abstract]
One year or less, Cost or Amortized Cost Basis	145,511		145,511
Excess of one year to five years, Cost or Amortized Cost Basis	155,127		155,127
Excess of five years to ten years, Cost or Amortized Cost Basis	46,078		46,078
Excess of ten years, Cost or Amortized Cost Basis	8,340		8,340
Contractual maturities, Cost or Amortized Cost Basis	355,056		355,056
Asset-backed securities, Cost or Amortized Cost Basis	76,111		76,111
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Limited partnerships - net gain (loss)	(1,064)	(211)	7,204	2,227
Net realized gains on investments	658	1,430	12,817	16,496
Available for sale securities gain loss activity [Abstract]
Realized net gains on the disposal of securities	2,223	1,090	5,837	11,888
Mark-to-market adjustment	(118)	342	151	747
Equity in gains (losses) of limited partnership investments - realized and unrealized	(1,064)	(211)	7,204	2,227
Write-downs based upon objective criteria	(441)	(4)	(546)	(78)
Recovery of prior write-downs upon sale or disposal	58	213	171	1,712
Net realized gains on investments	658	1,430	12,817	16,496
Net unrealized gain (loss) on investments	334		5,841
Net unrealized gains in limited partnership			13,305
Undistributed earnings of limited partnership, net of taxes	28,923		28,923
Committed funds for bridge loans	18,750		18,750
Number of bridge loan agreements	3		3
U.S. government obligations [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	123,933		123,933		113,389
Cost or amortized cost	123,859		123,859		113,348
Gross unrealized gains	125		125		81
Gross unrealized losses	(51)		(51)		(40)
Net unrealized gains (losses)	74		74		41
Residential mortgage-backed securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	7,349		7,349		13,252
Cost or amortized cost	7,084		7,084		12,058
Gross unrealized gains	322		322		1,334
Gross unrealized losses	(57)		(57)		(140)
Net unrealized gains (losses)	265		265		1,194
Commercial mortgage-backed securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	35,694		35,694		28,565
Cost or amortized cost	35,132		35,132		28,406
Gross unrealized gains	737		737		308
Gross unrealized losses	(175)		(175)		(149)
Net unrealized gains (losses)	562		562		159
States and municipal obligations [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	105,382		105,382		115,250
Cost or amortized cost	104,534		104,534		115,278
Gross unrealized gains	882		882		407
Gross unrealized losses	(34)		(34)		(435)
Net unrealized gains (losses)	848		848		(28)
Corporate securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	129,497		129,497		137,215
Cost or amortized cost	130,186		130,186		136,991
Gross unrealized gains	2,185		2,185		3,207
Gross unrealized losses	(2,874)		(2,874)		(2,983)
Net unrealized gains (losses)	(689)		(689)		224
Foreign government obligations [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	29,946		29,946		23,879
Cost or amortized cost	30,372		30,372		23,689
Gross unrealized gains	185		185		588
Gross unrealized losses	(611)		(611)		(398)
Net unrealized gains (losses)	(426)		(426)		190
Total fixed maturities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	431,801		431,801		431,550
Cost or amortized cost	431,167		431,167		429,770
Gross unrealized gains	4,436		4,436		5,925
Gross unrealized losses	(3,802)		(3,802)		(4,145)
Net unrealized gains (losses)	634		634		1,780
Available-for-sale securities continuous unrealized loss position [Abstract]
Number of Securities, 12 months or less	353		353		451
Number of Securities, Greater than 12 months	131		131		53
Number of Securities, total	484		484		504
Available-for-sale securities continuous unrealized loss position, Fair Value [Abstract]
Fair value, 12 months or less	90,946		90,946		123,145
Fair value, Greater than 12 months	44,616		44,616		18,249
Fair value, total	135,562		135,562		141,394
Available-for-sale securities continuous unrealized loss position, aggregate losses [Abstract]
Gross unrealized loss, 12 months or less			(2,127)		(3,105)
Gross unrealized loss, Greater than 12 months			(1,675)		(1,040)
Gross unrealized loss, total			(3,802)		(4,145)
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Gross gains	798	2,043	5,399	5,695
Gross losses	(1,259)	(1,277)	(3,411)	(3,497)
Net realized gains (losses)	(461)	766	1,988	2,198
Financial institutions [Member]
Available-for-sale Equity Securities, Amortized Cost Basis [Abstract]
Fair value	20,594		20,594		18,850
Cost or amortized cost	9,520		9,520		7,780
Gross unrealized gains	11,096		11,096		11,171
Gross unrealized losses	(22)		(22)		(101)
Net unrealized gains (losses)	11,074		11,074		11,070
Industrial & miscellaneous [Member]
Available-for-sale Equity Securities, Amortized Cost Basis [Abstract]
Fair value	139,676		139,676		126,978
Cost or amortized cost	67,077		67,077		64,307
Gross unrealized gains	73,467		73,467		63,009
Gross unrealized losses	(868)		(868)		(338)
Net unrealized gains (losses)	72,599		72,599		62,671
Total equity securities [Member]
Available-for-sale Equity Securities, Amortized Cost Basis [Abstract]
Fair value	160,270		160,270		145,828
Cost or amortized cost	76,597		76,597		72,087
Gross unrealized gains	84,563		84,563		74,180
Gross unrealized losses	(890)		(890)		(439)
Net unrealized gains (losses)	83,673		83,673		73,741
Available-for-sale securities continuous unrealized loss position [Abstract]
Number of Securities, 12 months or less	30		30		10
Number of Securities, Greater than 12 months	5		5		2
Number of Securities, total	35		35		12
Available-for-sale securities continuous unrealized loss position, Fair Value [Abstract]
Fair value, 12 months or less	9,248		9,248		1,682
Fair value, Greater than 12 months	1,516		1,516		1,980
Fair value, total	10,764		10,764		3,662
Available-for-sale securities continuous unrealized loss position, aggregate losses [Abstract]
Gross unrealized loss, 12 months or less			(806)		(204)
Gross unrealized loss, Greater than 12 months			(84)		(235)
Gross unrealized loss, total			(890)		(439)
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Gross gains	2,529	1,233	4,682	13,838
Gross losses	(346)	(358)	(1,057)	(1,767)
Net realized gains (losses)	2,183	875	3,625	12,071
Total available-for-sale securities [Member]
Available-for-sale Securities, Fair Value to Amortized Cost Basis [Abstract]
Fair value	592,071		592,071		577,378
Cost or amortized cost	507,764		507,764		501,857
Gross unrealized gains	88,999		88,999		80,105
Gross unrealized losses	(4,692)		(4,692)		(4,584)
Net unrealized gains (losses)	$ 84,307		$ 84,307		$ 75,521