Summary of Investments (Investments in Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013 issues	Dec. 31, 2012 issues
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	496	107
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 819,729	$ 182,504
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	39,551	2,568
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	45	66
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	45,326	37,565
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	2,886	2,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	865,055	220,069
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	42,437	4,568
Fixed Maturities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	485	91
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	815,745	181,198
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	39,306	2,386
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	29	34
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	43,517	32,783
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	2,623	1,482
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	859,262	213,981
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	41,929	3,868
U.S. Treasury [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	8	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	7,493	1,724
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	86	5
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	7,493	1,724
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	86	5
U.S. Government Agency [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	61	5
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	170,795	17,654
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	11,844	67
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	170,795	17,654
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	11,844	67
States, Municipalities and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	156	31
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	119,047	41,775
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	8,255	819
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	2	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	5,867	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	883	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	124,914	41,775
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	9,138	819
Foreign Bonds [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	9	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	23,867	3,323
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	324	48
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	0	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	558
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	0	14
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	23,867	3,881
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	324	62
Public Utilities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	27	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	52,241	3,155
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	947	32
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	52,241	3,155
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	947	32
Corporate Bonds [Member] | Energy [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	10
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	25,104
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	858
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	25,104
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	858
Corporate Bonds [Member] | Industrials [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	27	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	71,118	12,194
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	2,257	109
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	0	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	2,897
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	0	103
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	71,118	15,091
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	2,257	212
Corporate Bonds [Member] | Consumer Goods and Services [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	19	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	38,968	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	983	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	6	7
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	3,256	4,606
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	116	151
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	42,224	4,606
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	1,099	151
Corporate Bonds [Member] | Health Care [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	9	3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	25,008	7,416
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	963	80
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	1	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,181	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	111	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	26,189	7,416
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	1,074	80
Corporate Bonds [Member] | Technology, Media and Telecommunications [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	16	5
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	55,331	13,402
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	3,203	198
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	55,331	13,402
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	3,203	198
Corporate Bonds [Member] | Financial Services [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	6	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	17,773	1,005
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	699	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	2	24
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	6,513	24,693
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	64	1,058
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	24,286	25,698
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	763	1,059
Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	37	7
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	10,620	4,472
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	250	21
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	5	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	333	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	19	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	10,953	4,472
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	269	21
Collateralized Mortgage Obligations [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	100	27
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	198,380	74,702
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	8,637	1,004
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	13	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	26,367	29
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	1,430	156
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	224,747	74,731
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	10,067	1,160
Redeemable Preferred Stocks [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues		2
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		376
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation		2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		376
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation		2
Equity Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	11	16
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	3,984	1,306
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	245	182
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	16	32
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,809	4,782
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	263	518
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	5,793	6,088
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	508	700
Common Stocks [Member] | Public Utilities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	3	3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	267	225
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	41	83
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	267	225
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	41	83
Common Stocks [Member] | Industrials [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	0	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	482
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	0	52
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	3	9
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	140	621
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	59	122
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	140	1,103
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	59	174
Common Stocks [Member] | Consumer Goods and Services [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	0	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	280
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	0	19
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	2	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	66	372
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	10	31
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	66	652
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	10	50
Common Stocks [Member] | Health Care [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues		1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		31
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation		2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues		3
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		896
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation		123
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		927
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation		125
Common Stocks [Member] | Technology, Media and Telecommunications [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	4	5
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	245	241
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	2	7
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	6	7
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	227	581
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	62	88
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	472	822
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	64	95
Common Stocks [Member] | Financial Services [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	1	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	47	47
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	19	19
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	3	7
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	206	1,109
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	71	126
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	253	1,156
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	90	145
Nonredeemable Preferred Stocks [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities in Unrealized Loss Positions, Less than Twelve Months, Number of Issues	3	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	3,425	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Depreciation	183	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Issues	2	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,170	1,203
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Depreciation	61	28
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	4,595	1,203
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Depreciation	$ 244	$ 28