Summary of Investments (Investments in Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014 issues	Dec. 31, 2013 issues
Available-for-sale
Less than 12 months, Number of Issues	356	528
Less than 12 months, Fair Value	$ 630,046	$ 922,128
Less than 12 months, Gross Unrealized Depreciation	24,686	48,023
12 months or longer, Number of Issues	109	88
12 months or longer, Fair Value	140,849	110,914
12 months or longer, Gross Unrealized Depreciation	10,358	11,807
Total, Fair Value	770,895	1,033,042
Total, Gross Unrealized Depreciation	35,044	59,830
Fixed Maturities [Member]
Available-for-sale
Less than 12 months, Number of Issues	355	524
Less than 12 months, Fair Value	630,031	918,634
Less than 12 months, Gross Unrealized Depreciation	24,683	47,906
12 months or longer, Number of Issues	95	71
12 months or longer, Fair Value	139,100	108,961
12 months or longer, Gross Unrealized Depreciation	10,131	11,477
Total, Fair Value	769,131	1,027,595
Total, Gross Unrealized Depreciation	34,814	59,383
U.S. Treasury [Member]
Available-for-sale
Less than 12 months, Number of Issues	12	10
Less than 12 months, Fair Value	11,663	9,196
Less than 12 months, Gross Unrealized Depreciation	130	140
12 months or longer, Number of Issues	0	0
12 months or longer, Fair Value	0	0
12 months or longer, Gross Unrealized Depreciation	0	0
Total, Fair Value	11,663	9,196
Total, Gross Unrealized Depreciation	130	140
U.S. Government Agency [Member]
Available-for-sale
Less than 12 months, Number of Issues	75	101
Less than 12 months, Fair Value	194,814	256,203
Less than 12 months, Gross Unrealized Depreciation	11,330	18,019
12 months or longer, Number of Issues	2	2
12 months or longer, Fair Value	4,689	4,356
12 months or longer, Gross Unrealized Depreciation	311	644
Total, Fair Value	199,503	260,559
Total, Gross Unrealized Depreciation	11,641	18,663
States, Municipalities and Political Subdivisions [Member]
Available-for-sale
Less than 12 months, Number of Issues	108	136
Less than 12 months, Fair Value	89,654	97,950
Less than 12 months, Gross Unrealized Depreciation	3,227	7,423
12 months or longer, Number of Issues	37	29
12 months or longer, Fair Value	32,844	29,670
12 months or longer, Gross Unrealized Depreciation	1,964	3,282
Total, Fair Value	122,498	127,620
Total, Gross Unrealized Depreciation	5,191	10,705
Foreign Bonds [Member]
Available-for-sale
Less than 12 months, Number of Issues	3	10
Less than 12 months, Fair Value	6,231	20,832
Less than 12 months, Gross Unrealized Depreciation	104	397
12 months or longer, Number of Issues	0	0
12 months or longer, Fair Value	0	0
12 months or longer, Gross Unrealized Depreciation	0	0
Total, Fair Value	6,231	20,832
Total, Gross Unrealized Depreciation	104	397
Public Utilities [Member]
Available-for-sale
Less than 12 months, Number of Issues	23	31
Less than 12 months, Fair Value	46,900	61,582
Less than 12 months, Gross Unrealized Depreciation	764	1,776
12 months or longer, Number of Issues	0	0
12 months or longer, Fair Value	0	0
12 months or longer, Gross Unrealized Depreciation	0	0
Total, Fair Value	46,900	61,582
Total, Gross Unrealized Depreciation	764	1,776
Corporate Bonds [Member] | Energy [Member]
Available-for-sale
Less than 12 months, Number of Issues	7	9
Less than 12 months, Fair Value	17,647	23,735
Less than 12 months, Gross Unrealized Depreciation	395	1,008
12 months or longer, Number of Issues	1	0
12 months or longer, Fair Value	4,053	0
12 months or longer, Gross Unrealized Depreciation	287	0
Total, Fair Value	21,700	23,735
Total, Gross Unrealized Depreciation	682	1,008
Corporate Bonds [Member] | Industrials [Member]
Available-for-sale
Less than 12 months, Number of Issues	14	34
Less than 12 months, Fair Value	34,997	77,788
Less than 12 months, Gross Unrealized Depreciation	655	2,819
12 months or longer, Number of Issues	2	0
12 months or longer, Fair Value	7,482	0
12 months or longer, Gross Unrealized Depreciation	554	0
Total, Fair Value	42,479	77,788
Total, Gross Unrealized Depreciation	1,209	2,819
Corporate Bonds [Member] | Consumer Goods and Services [Member]
Available-for-sale
Less than 12 months, Number of Issues	10	31
Less than 12 months, Fair Value	28,316	58,833
Less than 12 months, Gross Unrealized Depreciation	363	1,276
12 months or longer, Number of Issues	7	6
12 months or longer, Fair Value	5,115	3,218
12 months or longer, Gross Unrealized Depreciation	234	145
Total, Fair Value	33,431	62,051
Total, Gross Unrealized Depreciation	597	1,421
Corporate Bonds [Member] | Health Care [Member]
Available-for-sale
Less than 12 months, Number of Issues	5	10
Less than 12 months, Fair Value	15,026	25,888
Less than 12 months, Gross Unrealized Depreciation	362	942
12 months or longer, Number of Issues	2	2
12 months or longer, Fair Value	4,480	4,427
12 months or longer, Gross Unrealized Depreciation	190	258
Total, Fair Value	19,506	30,315
Total, Gross Unrealized Depreciation	552	1,200
Corporate Bonds [Member] | Technology, Media and Telecommunications [Member]
Available-for-sale
Less than 12 months, Number of Issues	7	18
Less than 12 months, Fair Value	25,434	58,105
Less than 12 months, Gross Unrealized Depreciation	675	2,147
12 months or longer, Number of Issues	2	2
12 months or longer, Fair Value	7,782	7,468
12 months or longer, Gross Unrealized Depreciation	841	1,174
Total, Fair Value	33,216	65,573
Total, Gross Unrealized Depreciation	1,516	3,321
Corporate Bonds [Member] | Financial Services [Member]
Available-for-sale
Less than 12 months, Number of Issues	5	7
Less than 12 months, Fair Value	12,252	15,191
Less than 12 months, Gross Unrealized Depreciation	239	720
12 months or longer, Number of Issues	1	1
12 months or longer, Fair Value	505	1,525
12 months or longer, Gross Unrealized Depreciation	33	3
Total, Fair Value	12,757	16,716
Total, Gross Unrealized Depreciation	272	723
Mortgage-Backed Securities [Member]
Available-for-sale
Less than 12 months, Number of Issues	11	16
Less than 12 months, Fair Value	3,707	4,476
Less than 12 months, Gross Unrealized Depreciation	120	177
12 months or longer, Number of Issues	7	6
12 months or longer, Fair Value	3,086	3,113
12 months or longer, Gross Unrealized Depreciation	95	114
Total, Fair Value	6,793	7,589
Total, Gross Unrealized Depreciation	215	291
Collateralized Mortgage Obligations [Member]
Available-for-sale
Less than 12 months, Number of Issues	75	111
Less than 12 months, Fair Value	143,390	208,855
Less than 12 months, Gross Unrealized Depreciation	6,319	11,062
12 months or longer, Number of Issues	34	23
12 months or longer, Fair Value	69,064	55,184
12 months or longer, Gross Unrealized Depreciation	5,622	5,857
Total, Fair Value	212,454	264,039
Total, Gross Unrealized Depreciation	11,941	16,919
Equity Securities [Member]
Available-for-sale
Less than 12 months, Number of Issues	1	4
Less than 12 months, Fair Value	15	3,494
Less than 12 months, Gross Unrealized Depreciation	3	117
12 months or longer, Number of Issues	14	17
12 months or longer, Fair Value	1,749	1,953
12 months or longer, Gross Unrealized Depreciation	227	330
Total, Fair Value	1,764	5,447
Total, Gross Unrealized Depreciation	230	447
Common Stocks [Member] | Public Utilities [Member]
Available-for-sale
Less than 12 months, Number of Issues		0
Less than 12 months, Fair Value		0
Less than 12 months, Gross Unrealized Depreciation		0
12 months or longer, Number of Issues		3
12 months or longer, Fair Value		281
12 months or longer, Gross Unrealized Depreciation		27
Total, Fair Value		281
Total, Gross Unrealized Depreciation		27
Common Stocks [Member] | Industrials [Member]
Available-for-sale
Less than 12 months, Number of Issues	0	1
Less than 12 months, Fair Value	0	1
Less than 12 months, Gross Unrealized Depreciation	0	1
12 months or longer, Number of Issues	2	2
12 months or longer, Fair Value	78	81
12 months or longer, Gross Unrealized Depreciation	34	31
Total, Fair Value	78	82
Total, Gross Unrealized Depreciation	34	32
Common Stocks [Member] | Consumer Goods and Services [Member]
Available-for-sale
Less than 12 months, Number of Issues	1
Less than 12 months, Fair Value	15
Less than 12 months, Gross Unrealized Depreciation	3
12 months or longer, Number of Issues	0
12 months or longer, Fair Value	0
12 months or longer, Gross Unrealized Depreciation	0
Total, Fair Value	15
Total, Gross Unrealized Depreciation	3
Common Stocks [Member] | Technology, Media and Telecommunications [Member]
Available-for-sale
Less than 12 months, Number of Issues	0	0
Less than 12 months, Fair Value	0	0
Less than 12 months, Gross Unrealized Depreciation	0	0
12 months or longer, Number of Issues	6	6
12 months or longer, Fair Value	231	206
12 months or longer, Gross Unrealized Depreciation	58	83
Total, Fair Value	231	206
Total, Gross Unrealized Depreciation	58	83
Common Stocks [Member] | Financial Services [Member]
Available-for-sale
Less than 12 months, Number of Issues	0	0
Less than 12 months, Fair Value	0	0
Less than 12 months, Gross Unrealized Depreciation	0	0
12 months or longer, Number of Issues	4	4
12 months or longer, Fair Value	230	215
12 months or longer, Gross Unrealized Depreciation	113	128
Total, Fair Value	230	215
Total, Gross Unrealized Depreciation	113	128
Nonredeemable Preferred Stocks [Member]
Available-for-sale
Less than 12 months, Number of Issues	0	3
Less than 12 months, Fair Value	0	3,493
Less than 12 months, Gross Unrealized Depreciation	0	116
12 months or longer, Number of Issues	2	2
12 months or longer, Fair Value	1,210	1,170
12 months or longer, Gross Unrealized Depreciation	22	61
Total, Fair Value	1,210	4,663
Total, Gross Unrealized Depreciation	$ 22	$ 177