Fair Value of Financial Instruments (Financial Instruments Measured at Fiar Value) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	$ 3,010,431	$ 2,856,699
Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	3,010,431	2,856,699
Trading Securities	14,498	13,454
Short- Term Investments	800	1,100
Money Market Accounts	31,047	62,899
Total Assets Measured at Fair Value	3,056,776	2,934,152
Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	176,082	156,076
Trading Securities	2,633	1,659
Short- Term Investments	800	1,100
Money Market Accounts	31,047	62,899
Total Assets Measured at Fair Value	210,562	221,734
Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	2,810,127	2,674,781
Trading Securities	11,865	11,795
Short- Term Investments	0	0
Money Market Accounts	0	0
Total Assets Measured at Fair Value	2,821,992	2,686,576
Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	24,222	25,842
Trading Securities	0	0
Short- Term Investments	0	0
Money Market Accounts	0	0
Total Assets Measured at Fair Value	24,222	25,842
Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	2,830,707	2,697,248
Debt Securities [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	2,830,707	2,697,248
Debt Securities [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	382	409
Debt Securities [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	2,809,807	2,674,523
Debt Securities [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	20,518	22,316
U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	45,872	43,951
U.S. Treasury [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	45,872	43,951
U.S. Treasury [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
U.S. Treasury [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	45,872	43,951
U.S. Treasury [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
U.S. Government Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	28,297	96,395
U.S. Government Agency [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	28,297	96,395
U.S. Government Agency [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
U.S. Government Agency [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	28,297	96,395
U.S. Government Agency [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
States, Municipalities and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	774,676	748,107
States, Municipalities and Political Subdivisions [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	774,676	748,107
States, Municipalities and Political Subdivisions [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
States, Municipalities and Political Subdivisions [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	773,861	747,227
States, Municipalities and Political Subdivisions [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	815	880
Foreign Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	221,864	214,815
Foreign Bonds [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	221,864	214,815
Trading Securities	2,905	2,906
Foreign Bonds [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Trading Securities	0	0
Foreign Bonds [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	221,028	213,979
Trading Securities	2,905	2,906
Foreign Bonds [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	836	836
Trading Securities	0	0
Public Utilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	261,147	270,071
Public Utilities [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	261,147	270,071
Public Utilities [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Public Utilities [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	261,147	270,071
Public Utilities [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	31,895	35,390
Mortgage Backed Securities [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	31,895	35,390
Mortgage Backed Securities [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Mortgage Backed Securities [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	31,895	35,390
Mortgage Backed Securities [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	194,157	82,851
Collateralized Mortgage Obligations [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	194,157	82,851
Collateralized Mortgage Obligations [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Collateralized Mortgage Obligations [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	194,157	82,851
Collateralized Mortgage Obligations [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	4,986	6,296
Asset-Backed Securities [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	4,986	6,296
Asset-Backed Securities [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Asset-Backed Securities [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	2,397	5,981
Asset-Backed Securities [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	2,589	315
Redeemable Preferred Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	382	409
Redeemable Preferred Stocks [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	382	409
Trading Securities	2,633	3,075
Redeemable Preferred Stocks [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	382	409
Trading Securities	2,633	1,659
Redeemable Preferred Stocks [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Trading Securities	0	1,416
Redeemable Preferred Stocks [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Trading Securities	0	0
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	179,724	159,451
Equity Securities [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	179,724	159,451
Equity Securities [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	175,700	155,667
Equity Securities [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	320	258
Equity Securities [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	3,704	3,526
Nonredeemable Preferred Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	3,836	3,290
Nonredeemable Preferred Stocks [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	3,836	3,290
Nonredeemable Preferred Stocks [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	3,591	3,032
Nonredeemable Preferred Stocks [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	245	258
Nonredeemable Preferred Stocks [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Public Utilities [Member] | Common Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	14,502	14,735
Public Utilities [Member] | Common Stocks [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	14,502	14,735
Public Utilities [Member] | Common Stocks [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	14,502	14,735
Public Utilities [Member] | Common Stocks [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Public Utilities [Member] | Common Stocks [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Energy [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	183,435	197,192
Energy [Member] | Corporate Bonds [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	183,435	197,192
Energy [Member] | Corporate Bonds [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Energy [Member] | Corporate Bonds [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	183,435	197,192
Energy [Member] | Corporate Bonds [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Energy [Member] | Common Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	12,440	12,210
Energy [Member] | Common Stocks [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	12,440	12,210
Energy [Member] | Common Stocks [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	12,440	12,210
Energy [Member] | Common Stocks [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Energy [Member] | Common Stocks [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Industrial [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	315,914	295,677
Industrial [Member] | Corporate Bonds [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	315,914	295,677
Trading Securities	1,449	1,443
Industrial [Member] | Corporate Bonds [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Trading Securities	0	0
Industrial [Member] | Corporate Bonds [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	313,017	292,780
Trading Securities	1,449	1,443
Industrial [Member] | Corporate Bonds [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	2,897	2,897
Trading Securities	0	0
Industrial [Member] | Common Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	30,683	28,556
Industrial [Member] | Common Stocks [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	30,683	28,556
Industrial [Member] | Common Stocks [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	30,608	28,556
Industrial [Member] | Common Stocks [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	75	0
Industrial [Member] | Common Stocks [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Consumer Goods and Service [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	208,582	212,174
Consumer Goods and Service [Member] | Corporate Bonds [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	208,582	212,174
Trading Securities	1,557	1,059
Consumer Goods and Service [Member] | Corporate Bonds [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Trading Securities	0	0
Consumer Goods and Service [Member] | Corporate Bonds [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	207,222	210,759
Trading Securities	1,557	1,059
Consumer Goods and Service [Member] | Corporate Bonds [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	1,360	1,415
Trading Securities	0	0
Consumer Goods and Service [Member] | Common Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	18,895	18,564
Consumer Goods and Service [Member] | Common Stocks [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	18,895	18,564
Consumer Goods and Service [Member] | Common Stocks [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	18,895	18,564
Consumer Goods and Service [Member] | Common Stocks [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Consumer Goods and Service [Member] | Common Stocks [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Health Care [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	125,424	115,671
Health Care [Member] | Corporate Bonds [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	125,424	115,671
Trading Securities	2,120	1,450
Health Care [Member] | Corporate Bonds [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Trading Securities	0	0
Health Care [Member] | Corporate Bonds [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	125,424	115,671
Trading Securities	2,120	1,450
Health Care [Member] | Corporate Bonds [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Trading Securities	0	0
Health Care [Member] | Common Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	19,142	15,988
Health Care [Member] | Common Stocks [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	19,142	15,988
Health Care [Member] | Common Stocks [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	19,142	15,988
Health Care [Member] | Common Stocks [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Health Care [Member] | Common Stocks [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Technology, Media and Telecommunications [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	134,870	112,948
Technology, Media and Telecommunications [Member] | Corporate Bonds [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	134,870	112,948
Trading Securities	2,388	1,458
Technology, Media and Telecommunications [Member] | Corporate Bonds [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Trading Securities	0	0
Technology, Media and Telecommunications [Member] | Corporate Bonds [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	134,870	112,948
Trading Securities	2,388	1,458
Technology, Media and Telecommunications [Member] | Corporate Bonds [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Trading Securities	0	0
Technology, Media and Telecommunications [Member] | Common Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	11,156	10,018
Technology, Media and Telecommunications [Member] | Common Stocks [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	11,156	10,018
Technology, Media and Telecommunications [Member] | Common Stocks [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	11,156	10,018
Technology, Media and Telecommunications [Member] | Common Stocks [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Technology, Media and Telecommunications [Member] | Common Stocks [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Financial Services [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	299,206	265,301
Financial Services [Member] | Corporate Bonds [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	299,206	265,301
Trading Securities	1,446	2,063
Financial Services [Member] | Corporate Bonds [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Trading Securities	0	0
Financial Services [Member] | Corporate Bonds [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	287,185	249,328
Trading Securities	1,446	2,063
Financial Services [Member] | Corporate Bonds [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	12,021	15,973
Trading Securities	0	0
Financial Services [Member] | Common Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	69,070	56,090
Financial Services [Member] | Common Stocks [Member] | Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	69,070	56,090
Financial Services [Member] | Common Stocks [Member] | Level 1 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	65,366	52,564
Financial Services [Member] | Common Stocks [Member] | Level 2 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	0	0
Financial Services [Member] | Common Stocks [Member] | Level 3 [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-For-Sale Securities	$ 3,704	$ 3,526