Investments (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($) Security Borrower Agreement	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) Security Borrower Agreement	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) Security
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Cost or amortized cost	$ 438,712		$ 438,712
Available-for-sale Securities, Fair Value to Amortized Cost Basis [Abstract]
Applicable federal income taxes			(28,438)		$ (27,913)
Net unrealized gains - net of tax			$ 52,814		$ 51,840
Available-for-sale securities continuous unrealized loss position [Abstract]
Number of Securities, total | Security	596		596		767
Available-for-sale securities continuous unrealized loss position, Fair Value [Abstract]
Fair value, total	$ 145,660		$ 145,660		$ 218,647
Available-for-sale securities continuous unrealized loss position, aggregate losses [Abstract]
Gross unrealized loss, total	(9,493)		(9,493)		(9,724)
Available-for-sale securities debt maturities fair value [Abstract]
One year or less, Fair Value	78,160		78,160
Excess of one year to five years, Fair Value	233,736		233,736
Excess of five years to ten years, Fair Value	33,286		33,286
Excess of ten years, Fair Value	9,466		9,466
Contractual maturities, Fair Value	354,648		354,648
Asset-backed securities, Fair Value	81,634		81,634
Total, Fair Value	436,282		436,282
Available-for-sale securities debt maturities amortized cost basis [Abstract]
One year or less, Cost or Amortized Cost Basis	78,494		78,494
Excess of one year to five years, Cost or Amortized Cost Basis	236,830		236,830
Excess of five years to ten years, Cost or Amortized Cost Basis	33,862		33,862
Excess of ten years, Cost or Amortized Cost Basis	9,207		9,207
Contractual maturities, Cost or Amortized Cost Basis	358,393		358,393
Asset-backed securities, Cost or Amortized Cost Basis	80,319		80,319
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Limited partnerships - net gain (loss)	(293)	$ 5,200	4,240	$ 8,268
Net realized gains (losses) on investments	(1,166)	8,089	2,577	12,159
Available for sale securities gain loss activity [Abstract]
Realized net gains (losses) on the disposal of securities	(125)	2,419	(413)	3,614
Mark-to-market adjustment	(104)	469	(392)	269
Equity in gains (losses) of limited partnership investments - realized and unrealized	(293)	5,200	4,240	8,268
Write-downs based upon objective criteria	(893)	0	(1,107)	(105)
Recovery of prior write-downs upon sale or disposal	249	1	249	113
Net realized gains (losses) on investments	(1,166)	8,089	2,577	12,159
Net unrealized gains (losses) on investments	(931)		1,055
Net unrealized gains in limited partnership			14,303
Undistributed earnings of limited partnership, net of taxes	30,487		30,487
Committed funds for bridge loans	$ 11,000		$ 11,000
Number of separate borrowers related to bridge loan agreements | Borrower	2		2
Number of bridge loan agreements | Agreement	2		2
U.S. government obligations [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	$ 119,957		$ 119,957		101,094
Cost or amortized cost	119,692		119,692		101,058
Gross unrealized gains	281		281		108
Gross unrealized losses	(16)		(16)		(72)
Net unrealized gains (losses)	265		265		36
Residential mortgage-backed securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	5,676		5,676		6,066
Cost or amortized cost	5,478		5,478		5,830
Gross unrealized gains	230		230		273
Gross unrealized losses	(32)		(32)		(37)
Net unrealized gains (losses)	198		198		236
Commercial mortgage-backed securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	32,695		32,695		36,440
Cost or amortized cost	32,326		32,326		36,210
Gross unrealized gains	611		611		630
Gross unrealized losses	(242)		(242)		(400)
Net unrealized gains (losses)	369		369		230
States and municipal obligations [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	109,020		109,020		113,777
Cost or amortized cost	108,808		108,808		113,133
Gross unrealized gains	695		695		784
Gross unrealized losses	(483)		(483)		(140)
Net unrealized gains (losses)	212		212		644
Corporate securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	146,840		146,840		166,966
Cost or amortized cost	149,364		149,364		170,822
Gross unrealized gains	2,796		2,796		2,005
Gross unrealized losses	(5,320)		(5,320)		(5,861)
Net unrealized gains (losses)	(2,524)		(2,524)		(3,856)
Foreign government obligations [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	22,094		22,094		27,466
Cost or amortized cost	23,044		23,044		28,332
Gross unrealized gains	133		133		114
Gross unrealized losses	(1,083)		(1,083)		(980)
Net unrealized gains (losses)	(950)		(950)		(866)
Total fixed maturities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Fair value	436,282		436,282		451,809
Cost or amortized cost	438,712		438,712		455,385
Gross unrealized gains	4,746		4,746		3,914
Gross unrealized losses	(7,176)		(7,176)		(7,490)
Net unrealized gains (losses)	$ (2,430)		$ (2,430)		$ (3,576)
Available-for-sale securities continuous unrealized loss position [Abstract]
Number of Securities, 12 months or less | Security	449		449		591
Number of Securities, Greater than 12 months | Security	91		91		140
Number of Securities, total | Security	540		540		731
Available-for-sale securities continuous unrealized loss position, Fair Value [Abstract]
Fair value, 12 months or less	$ 106,272		$ 106,272		$ 176,756
Fair value, Greater than 12 months	20,054		20,054		27,667
Fair value, total	126,326		126,326		204,423
Available-for-sale securities continuous unrealized loss position, aggregate losses [Abstract]
Gross unrealized loss, 12 months or less	(5,984)		(5,984)		(6,083)
Gross unrealized loss, Greater than 12 months	(1,192)		(1,192)		(1,407)
Gross unrealized loss, total	(7,176)		(7,176)		(7,490)
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Gross gains	985	2,762	2,132	4,601
Gross losses	(1,856)	(926)	(3,789)	(2,152)
Net realized gains (losses)	(871)	1,836	(1,657)	2,449
Financial institutions [Member]
Available-for-sale Equity Securities, Amortized Cost Basis [Abstract]
Fair value	25,324		25,324		25,343
Cost or amortized cost	9,827		9,827		10,100
Gross unrealized gains	15,511		15,511		15,303
Gross unrealized losses	(14)		(14)		(60)
Net unrealized gains (losses)	15,497		15,497		15,243
Industrial & miscellaneous [Member]
Available-for-sale Equity Securities, Amortized Cost Basis [Abstract]
Fair value	147,312		147,312		136,764
Cost or amortized cost	79,127		79,127		68,678
Gross unrealized gains	70,488		70,488		70,260
Gross unrealized losses	(2,303)		(2,303)		(2,174)
Net unrealized gains (losses)	68,185		68,185		68,086
Total equity securities [Member]
Available-for-sale Equity Securities, Amortized Cost Basis [Abstract]
Fair value	172,636		172,636		162,107
Cost or amortized cost	88,954		88,954		78,778
Gross unrealized gains	85,999		85,999		85,563
Gross unrealized losses	(2,317)		(2,317)		(2,234)
Net unrealized gains (losses)	$ 83,682		$ 83,682		$ 83,329
Available-for-sale securities continuous unrealized loss position [Abstract]
Number of Securities, 12 months or less | Security	50		50		33
Number of Securities, Greater than 12 months | Security	6		6		3
Number of Securities, total | Security	56		56		36
Available-for-sale securities continuous unrealized loss position, Fair Value [Abstract]
Fair value, 12 months or less	$ 18,174		$ 18,174		$ 13,538
Fair value, Greater than 12 months	1,160		1,160		686
Fair value, total	19,334		19,334		14,224
Available-for-sale securities continuous unrealized loss position, aggregate losses [Abstract]
Gross unrealized loss, 12 months or less	(2,282)		(2,282)		(2,170)
Gross unrealized loss, Greater than 12 months	(35)		(35)		(64)
Gross unrealized loss, total	(2,317)		(2,317)		(2,234)
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Gross gains	1,230	1,412	1,979	2,153
Gross losses	(1,232)	(359)	(1,985)	(711)
Net realized gains (losses)	(2)	$ 1,053	(6)	$ 1,442
Total available-for-sale securities [Member]
Available-for-sale Securities, Fair Value to Amortized Cost Basis [Abstract]
Fair value	608,918		608,918		613,916
Cost or amortized cost	527,666		527,666		534,163
Gross unrealized gains	90,745		90,745		89,477
Gross unrealized losses	(9,493)		(9,493)		(9,724)
Net unrealized gains (losses)	$ 81,252		$ 81,252		$ 79,753