Fair Value of Financial Instruments (Financial Instruments Measured at Fair Value) (Details) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2015 USD ($) security	Jun. 30, 2015 USD ($) security	Dec. 31, 2014 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	$ 3,055,908	$ 3,055,908	$ 3,088,922
Trading Securities	$ 19,987	$ 19,987	20,928
Number of securities transferred between Level 1 and 2 \| security	0	0
Fixed Maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	$ 2,811,361	$ 2,811,361	2,843,079
U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	20,915	20,915	25,972
U.S. Government Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	267,313	267,313	351,672
States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| Midwest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	165,128	165,128	185,920
States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| Northeast [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	56,645	56,645	61,154
States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| South [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	128,315	128,315	126,220
States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| West [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	97,153	97,153	78,433
States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| Midwest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	148,814	148,814	131,402
States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| Northeast [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	19,906	19,906	12,631
States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| South [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	106,052	106,052	111,222
States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| West [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	79,531	79,531	71,303
Foreign Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	105,194	105,194	140,173
Public Utilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	203,736	203,736	212,357
Corporate Bonds [Member] \| Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	115,590	115,590	137,133
Corporate Bonds [Member] \| Industrials [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	222,604	222,604	215,475
Corporate Bonds [Member] \| Consumer Goods and Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	183,508	183,508	177,001
Corporate Bonds [Member] \| Health Care [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	94,971	94,971	89,035
Corporate Bonds [Member] \| Technology, Media and Telecommunications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	145,334	145,334	134,529
Corporate Bonds [Member] \| Financial Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	261,167	261,167	223,582
Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	15,521	15,521	17,558
Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	368,008	368,008	337,289
Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	5,956	5,956	3,018
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	244,547	244,547	245,843
Common Stocks [Member] \| Public Utilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	17,512	17,512	20,290
Common Stocks [Member] \| Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	13,104	13,104	13,717
Common Stocks [Member] \| Industrials [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	46,670	46,670	45,459
Common Stocks [Member] \| Consumer Goods and Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	22,750	22,750	23,314
Common Stocks [Member] \| Health Care [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	32,353	32,353	30,356
Common Stocks [Member] \| Technology, Media and Telecommunications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	13,207	13,207	13,995
Common Stocks [Member] \| Financial Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	94,495	94,495	93,663
Nonredeemable Preferred Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	4,456	4,456	5,049
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	3,055,908	3,055,908	3,088,922
Trading Securities	19,987	19,987	20,928
Short-Term Investments	175	175	175
Money Market Accounts	39,693	39,693	28,095
Corporate-Owned Life Insurance	1,148	1,148	918
Total Assets Measured at Fair Value	3,116,911	3,116,911	3,139,038
Recurring [Member] \| Fixed Maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	2,811,361	2,811,361	2,843,079
Recurring [Member] \| U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	20,915	20,915	25,972
Recurring [Member] \| U.S. Government Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	267,313	267,313	351,672
Recurring [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| Midwest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	165,128	165,128	185,920
Recurring [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| Northeast [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	56,645	56,645	61,154
Recurring [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| South [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	128,315	128,315	126,220
Recurring [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| West [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	97,153	97,153	78,433
Recurring [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| Midwest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	148,814	148,814	131,402
Recurring [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| Northeast [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	19,906	19,906	12,631
Recurring [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| South [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	106,052	106,052	111,222
Recurring [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| West [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	79,531	79,531	71,303
Recurring [Member] \| Foreign Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	105,194	105,194	140,173
Recurring [Member] \| Public Utilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	203,736	203,736	212,357
Recurring [Member] \| Corporate Bonds [Member] \| Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	115,590	115,590	137,133
Recurring [Member] \| Corporate Bonds [Member] \| Industrials [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	222,604	222,604	215,475
Trading Securities	3,668	3,668	3,352
Recurring [Member] \| Corporate Bonds [Member] \| Consumer Goods and Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	183,508	183,508	177,001
Trading Securities	111	111
Recurring [Member] \| Corporate Bonds [Member] \| Health Care [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	94,971	94,971	89,035
Trading Securities	2,609	2,609	2,425
Recurring [Member] \| Corporate Bonds [Member] \| Technology, Media and Telecommunications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	145,334	145,334	134,529
Trading Securities	323	323	338
Recurring [Member] \| Corporate Bonds [Member] \| Financial Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	261,167	261,167	223,582
Trading Securities	5,540	5,540	5,997
Recurring [Member] \| Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	15,521	15,521	17,558
Recurring [Member] \| Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	368,008	368,008	337,289
Recurring [Member] \| Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	5,956	5,956	3,018
Recurring [Member] \| Redeemable Preferred Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	4,137	4,137	4,750
Recurring [Member] \| Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	244,547	244,547	245,843
Recurring [Member] \| Equity Securities [Member] \| Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	378	378	411
Recurring [Member] \| Equity Securities [Member] \| Consumer Goods and Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	1,000	1,000	1,034
Recurring [Member] \| Equity Securities [Member] \| Health Care [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	328	328	327
Recurring [Member] \| Equity Securities [Member] \| Technology, Media and Telecommunications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	365	365	411
Recurring [Member] \| Common Stocks [Member] \| Public Utilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	17,512	17,512	20,290
Recurring [Member] \| Common Stocks [Member] \| Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	13,104	13,104	13,717
Recurring [Member] \| Common Stocks [Member] \| Industrials [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	46,670	46,670	45,459
Recurring [Member] \| Common Stocks [Member] \| Consumer Goods and Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	22,750	22,750	23,314
Recurring [Member] \| Common Stocks [Member] \| Health Care [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	32,353	32,353	30,356
Recurring [Member] \| Common Stocks [Member] \| Technology, Media and Telecommunications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	13,207	13,207	13,995
Recurring [Member] \| Common Stocks [Member] \| Financial Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	94,495	94,495	93,663
Recurring [Member] \| Nonredeemable Preferred Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	4,456	4,456	5,049
Trading Securities	1,528	1,528	1,883
Recurring [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	236,590	236,590	237,407
Trading Securities	7,736	7,736	8,816
Short-Term Investments	175	175	175
Money Market Accounts	39,693	39,693	28,095
Corporate-Owned Life Insurance	0	0	0
Total Assets Measured at Fair Value	284,194	284,194	274,493
Recurring [Member] \| Level 1 [Member] \| Fixed Maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| U.S. Government Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| Midwest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| Northeast [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| South [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| West [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| Midwest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| Northeast [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| South [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| West [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| Foreign Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| Public Utilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| Corporate Bonds [Member] \| Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| Corporate Bonds [Member] \| Industrials [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Trading Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| Corporate Bonds [Member] \| Consumer Goods and Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Trading Securities	0	0
Recurring [Member] \| Level 1 [Member] \| Corporate Bonds [Member] \| Health Care [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Trading Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| Corporate Bonds [Member] \| Technology, Media and Telecommunications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Trading Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| Corporate Bonds [Member] \| Financial Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Trading Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 1 [Member] \| Redeemable Preferred Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	4,137	4,137	4,750
Recurring [Member] \| Level 1 [Member] \| Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	236,590	236,590	237,407
Recurring [Member] \| Level 1 [Member] \| Equity Securities [Member] \| Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	378	378	411
Recurring [Member] \| Level 1 [Member] \| Equity Securities [Member] \| Consumer Goods and Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	1,000	1,000	1,034
Recurring [Member] \| Level 1 [Member] \| Equity Securities [Member] \| Health Care [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	328	328	327
Recurring [Member] \| Level 1 [Member] \| Equity Securities [Member] \| Technology, Media and Telecommunications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	365	365	411
Recurring [Member] \| Level 1 [Member] \| Common Stocks [Member] \| Public Utilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	17,512	17,512	20,290
Recurring [Member] \| Level 1 [Member] \| Common Stocks [Member] \| Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	13,104	13,104	13,717
Recurring [Member] \| Level 1 [Member] \| Common Stocks [Member] \| Industrials [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	46,668	46,668	45,458
Recurring [Member] \| Level 1 [Member] \| Common Stocks [Member] \| Consumer Goods and Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	22,750	22,750	23,314
Recurring [Member] \| Level 1 [Member] \| Common Stocks [Member] \| Health Care [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	32,353	32,353	30,356
Recurring [Member] \| Level 1 [Member] \| Common Stocks [Member] \| Technology, Media and Telecommunications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	13,207	13,207	13,995
Recurring [Member] \| Level 1 [Member] \| Common Stocks [Member] \| Financial Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	90,440	90,440	89,719
Recurring [Member] \| Level 1 [Member] \| Nonredeemable Preferred Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	556	556	558
Trading Securities	1,528	1,528	1,883
Recurring [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	2,801,655	2,801,655	2,833,200
Trading Securities	12,251	12,251	12,112
Short-Term Investments	0	0	0
Money Market Accounts	0	0	0
Corporate-Owned Life Insurance	1,148	1,148	918
Total Assets Measured at Fair Value	2,815,054	2,815,054	2,846,230
Recurring [Member] \| Level 2 [Member] \| Fixed Maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	2,797,676	2,797,676	2,828,636
Recurring [Member] \| Level 2 [Member] \| U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	20,915	20,915	25,972
Recurring [Member] \| Level 2 [Member] \| U.S. Government Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	267,313	267,313	351,672
Recurring [Member] \| Level 2 [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| Midwest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	165,128	165,128	185,920
Recurring [Member] \| Level 2 [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| Northeast [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	56,645	56,645	61,154
Recurring [Member] \| Level 2 [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| South [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	128,315	128,315	126,220
Recurring [Member] \| Level 2 [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| West [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	97,153	97,153	78,433
Recurring [Member] \| Level 2 [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| Midwest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	148,384	148,384	130,883
Recurring [Member] \| Level 2 [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| Northeast [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	19,906	19,906	12,631
Recurring [Member] \| Level 2 [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| South [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	106,052	106,052	111,222
Recurring [Member] \| Level 2 [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| West [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	79,531	79,531	71,303
Recurring [Member] \| Level 2 [Member] \| Foreign Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	105,194	105,194	140,173
Recurring [Member] \| Level 2 [Member] \| Public Utilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	203,736	203,736	212,357
Recurring [Member] \| Level 2 [Member] \| Corporate Bonds [Member] \| Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	115,590	115,590	137,133
Recurring [Member] \| Level 2 [Member] \| Corporate Bonds [Member] \| Industrials [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	222,604	222,604	215,475
Trading Securities	3,668	3,668	3,352
Recurring [Member] \| Level 2 [Member] \| Corporate Bonds [Member] \| Consumer Goods and Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	182,195	182,195	175,682
Trading Securities	111	111
Recurring [Member] \| Level 2 [Member] \| Corporate Bonds [Member] \| Health Care [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	94,971	94,971	89,035
Trading Securities	2,609	2,609	2,425
Recurring [Member] \| Level 2 [Member] \| Corporate Bonds [Member] \| Technology, Media and Telecommunications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	145,334	145,334	134,529
Trading Securities	323	323	338
Recurring [Member] \| Level 2 [Member] \| Corporate Bonds [Member] \| Financial Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	250,536	250,536	212,589
Trading Securities	5,540	5,540	5,997
Recurring [Member] \| Level 2 [Member] \| Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	15,521	15,521	17,558
Recurring [Member] \| Level 2 [Member] \| Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	368,008	368,008	337,289
Recurring [Member] \| Level 2 [Member] \| Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	4,645	4,645	1,406
Recurring [Member] \| Level 2 [Member] \| Redeemable Preferred Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	0	0	0
Recurring [Member] \| Level 2 [Member] \| Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	3,979	3,979	4,564
Recurring [Member] \| Level 2 [Member] \| Equity Securities [Member] \| Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	0	0	0
Recurring [Member] \| Level 2 [Member] \| Equity Securities [Member] \| Consumer Goods and Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	0	0	0
Recurring [Member] \| Level 2 [Member] \| Equity Securities [Member] \| Health Care [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	0	0	0
Recurring [Member] \| Level 2 [Member] \| Equity Securities [Member] \| Technology, Media and Telecommunications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	0	0	0
Recurring [Member] \| Level 2 [Member] \| Common Stocks [Member] \| Public Utilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 2 [Member] \| Common Stocks [Member] \| Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 2 [Member] \| Common Stocks [Member] \| Industrials [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	2	2	1
Recurring [Member] \| Level 2 [Member] \| Common Stocks [Member] \| Consumer Goods and Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 2 [Member] \| Common Stocks [Member] \| Health Care [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 2 [Member] \| Common Stocks [Member] \| Technology, Media and Telecommunications [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 2 [Member] \| Common Stocks [Member] \| Financial Services [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	77	77	72
Recurring [Member] \| Level 2 [Member] \| Nonredeemable Preferred Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	3,900	3,900	4,491
Trading Securities	0	0	0
Recurring [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	17,663	17,663	18,315
Trading Securities	0	0	0
Short-Term Investments	0	0	0
Money Market Accounts	0	0	0
Corporate-Owned Life Insurance	0	0	0
Total Assets Measured at Fair Value	17,663	17,663	18,315
Recurring [Member] \| Level 3 [Member] \| Fixed Maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	13,685	13,685	14,443
Recurring [Member] \| Level 3 [Member] \| U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 3 [Member] \| U.S. Government Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 3 [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| Midwest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 3 [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| Northeast [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 3 [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| South [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 3 [Member] \| States, Municipalities and Political Subdivisions [Member] \| General Obligations [Member] \| West [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 3 [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| Midwest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	430	430	519
Recurring [Member] \| Level 3 [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| Northeast [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-Sale Securities	0	0	0
Recurring [Member] \| Level 3 [Member] \| States, Municipalities and Political Subdivisions [Member] \| Special Revenue [Member] \| South [Member]

Fair Value of Financial Instruments (Financial Instruments Measured at Fair Value) (Details)
$ in Thousands

3 Months Ended

6 Months Ended

Jun. 30, 2015

USD ($)

security

Jun. 30, 2015

USD ($)

security

Dec. 31, 2014

USD ($)

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]