Summary of Investments (Investments in Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014 issue	Dec. 31, 2013 issue
Available-for-sale
Less than 12 months, Number of Issues	143	528
Less than 12 months, Fair Value	$ 267,797	$ 922,128
Less than 12 months, Gross Unrealized Depreciation	2,097	48,023
12 months or longer, Number of Issues	228	88
12 months or longer, Fair Value	410,008	110,914
12 months or longer, Gross Unrealized Depreciation	18,306	11,807
Total, Fair Value	677,805	1,033,042
Total, Gross Unrealized Depreciation	20,403	59,830
Fixed Maturities [Member]
Available-for-sale
Less than 12 months, Number of Issues	137	524
Less than 12 months, Fair Value	267,213	918,634
Less than 12 months, Gross Unrealized Depreciation	2,025	47,906
12 months or longer, Number of Issues	220	71
12 months or longer, Fair Value	409,035	108,961
12 months or longer, Gross Unrealized Depreciation	18,197	11,477
Total, Fair Value	676,248	1,027,595
Total, Gross Unrealized Depreciation	20,222	59,383
U.S. Treasury [Member]
Available-for-sale
Less than 12 months, Number of Issues	9	10
Less than 12 months, Fair Value	9,269	9,196
Less than 12 months, Gross Unrealized Depreciation	52	140
12 months or longer, Number of Issues	6	0
12 months or longer, Fair Value	6,086	0
12 months or longer, Gross Unrealized Depreciation	77	0
Total, Fair Value	15,355	9,196
Total, Gross Unrealized Depreciation	129	140
U.S. Government Agency [Member]
Available-for-sale
Less than 12 months, Number of Issues	34	101
Less than 12 months, Fair Value	89,312	256,203
Less than 12 months, Gross Unrealized Depreciation	532	18,019
12 months or longer, Number of Issues	44	2
12 months or longer, Fair Value	126,509	4,356
12 months or longer, Gross Unrealized Depreciation	5,715	644
Total, Fair Value	215,821	260,559
Total, Gross Unrealized Depreciation	6,247	18,663
States, Municipalities and Political Subdivisions [Member]
Available-for-sale
Less than 12 months, Number of Issues	20	136
Less than 12 months, Fair Value	21,590	97,950
Less than 12 months, Gross Unrealized Depreciation	107	7,423
12 months or longer, Number of Issues	71	29
12 months or longer, Fair Value	60,745	29,670
12 months or longer, Gross Unrealized Depreciation	1,195	3,282
Total, Fair Value	82,335	127,620
Total, Gross Unrealized Depreciation	1,302	10,705
Foreign Bonds [Member]
Available-for-sale
Less than 12 months, Number of Issues		10
Less than 12 months, Fair Value		20,832
Less than 12 months, Gross Unrealized Depreciation		397
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		20,832
Total, Gross Unrealized Depreciation		397
Public Utilities [Member]
Available-for-sale
Less than 12 months, Number of Issues	14	31
Less than 12 months, Fair Value	25,296	61,582
Less than 12 months, Gross Unrealized Depreciation	159	1,776
12 months or longer, Number of Issues	5	0
12 months or longer, Fair Value	5,261	0
12 months or longer, Gross Unrealized Depreciation	136	0
Total, Fair Value	30,557	61,582
Total, Gross Unrealized Depreciation	295	1,776
Corporate Bonds [Member] | Energy [Member]
Available-for-sale
Less than 12 months, Number of Issues	5	9
Less than 12 months, Fair Value	10,680	23,735
Less than 12 months, Gross Unrealized Depreciation	32	1,008
12 months or longer, Number of Issues	3	0
12 months or longer, Fair Value	7,170	0
12 months or longer, Gross Unrealized Depreciation	282	0
Total, Fair Value	17,850	23,735
Total, Gross Unrealized Depreciation	314	1,008
Corporate Bonds [Member] | Industrials [Member]
Available-for-sale
Less than 12 months, Number of Issues	5	34
Less than 12 months, Fair Value	10,977	77,788
Less than 12 months, Gross Unrealized Depreciation	69	2,819
12 months or longer, Number of Issues	4	0
12 months or longer, Fair Value	13,347	0
12 months or longer, Gross Unrealized Depreciation	1,153	0
Total, Fair Value	24,324	77,788
Total, Gross Unrealized Depreciation	1,222	2,819
Corporate Bonds [Member] | Consumer Goods and Services [Member]
Available-for-sale
Less than 12 months, Number of Issues	4	31
Less than 12 months, Fair Value	12,349	58,833
Less than 12 months, Gross Unrealized Depreciation	200	1,276
12 months or longer, Number of Issues	8	6
12 months or longer, Fair Value	15,447	3,218
12 months or longer, Gross Unrealized Depreciation	195	145
Total, Fair Value	27,796	62,051
Total, Gross Unrealized Depreciation	395	1,421
Corporate Bonds [Member] | Health Care [Member]
Available-for-sale
Less than 12 months, Number of Issues	3	10
Less than 12 months, Fair Value	7,489	25,888
Less than 12 months, Gross Unrealized Depreciation	85	942
12 months or longer, Number of Issues	3	2
12 months or longer, Fair Value	7,110	4,427
12 months or longer, Gross Unrealized Depreciation	196	258
Total, Fair Value	14,599	30,315
Total, Gross Unrealized Depreciation	281	1,200
Corporate Bonds [Member] | Technology, Media and Telecommunications [Member]
Available-for-sale
Less than 12 months, Number of Issues	6	18
Less than 12 months, Fair Value	17,577	58,105
Less than 12 months, Gross Unrealized Depreciation	174	2,147
12 months or longer, Number of Issues	5	2
12 months or longer, Fair Value	18,942	7,468
12 months or longer, Gross Unrealized Depreciation	889	1,174
Total, Fair Value	36,519	65,573
Total, Gross Unrealized Depreciation	1,063	3,321
Corporate Bonds [Member] | Financial Services [Member]
Available-for-sale
Less than 12 months, Number of Issues	8	7
Less than 12 months, Fair Value	15,185	15,191
Less than 12 months, Gross Unrealized Depreciation	79	720
12 months or longer, Number of Issues	2	1
12 months or longer, Fair Value	6,047	1,525
12 months or longer, Gross Unrealized Depreciation	145	3
Total, Fair Value	21,232	16,716
Total, Gross Unrealized Depreciation	224	723
Mortgage-Backed Securities [Member]
Available-for-sale
Less than 12 months, Number of Issues	5	16
Less than 12 months, Fair Value	217	4,476
Less than 12 months, Gross Unrealized Depreciation	15	177
12 months or longer, Number of Issues	5	6
12 months or longer, Fair Value	5,496	3,113
12 months or longer, Gross Unrealized Depreciation	105	114
Total, Fair Value	5,713	7,589
Total, Gross Unrealized Depreciation	120	291
Collateralized Mortgage Obligations [Member]
Available-for-sale
Less than 12 months, Number of Issues	24	111
Less than 12 months, Fair Value	47,272	208,855
Less than 12 months, Gross Unrealized Depreciation	521	11,062
12 months or longer, Number of Issues	64	23
12 months or longer, Fair Value	136,875	55,184
12 months or longer, Gross Unrealized Depreciation	8,109	5,857
Total, Fair Value	184,147	264,039
Total, Gross Unrealized Depreciation	8,630	16,919
Equity Securities [Member]
Available-for-sale
Less than 12 months, Number of Issues	6	4
Less than 12 months, Fair Value	584	3,494
Less than 12 months, Gross Unrealized Depreciation	72	117
12 months or longer, Number of Issues	8	17
12 months or longer, Fair Value	973	1,953
12 months or longer, Gross Unrealized Depreciation	109	330
Total, Fair Value	1,557	5,447
Total, Gross Unrealized Depreciation	181	447
Common Stocks [Member] | Public Utilities [Member]
Available-for-sale
Less than 12 months, Number of Issues	3	0
Less than 12 months, Fair Value	298	0
Less than 12 months, Gross Unrealized Depreciation	10	0
12 months or longer, Number of Issues	0	3
12 months or longer, Fair Value	0	281
12 months or longer, Gross Unrealized Depreciation	0	27
Total, Fair Value	298	281
Total, Gross Unrealized Depreciation	10	27
Common Stocks [Member] | Industrials [Member]
Available-for-sale
Less than 12 months, Number of Issues	1	1
Less than 12 months, Fair Value	49	1
Less than 12 months, Gross Unrealized Depreciation	3	1
12 months or longer, Number of Issues	2	2
12 months or longer, Fair Value	61	81
12 months or longer, Gross Unrealized Depreciation	52	31
Total, Fair Value	110	82
Total, Gross Unrealized Depreciation	55	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	14
Less than 12 months, Gross Unrealized Depreciation	4
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	14
Total, Gross Unrealized Depreciation	4
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	5	6
12 months or longer, Fair Value	211	206
12 months or longer, Gross Unrealized Depreciation	51	83
Total, Fair Value	211	206
Total, Gross Unrealized Depreciation	51	83
Common Stocks [Member] | Financial Services [Member]
Available-for-sale
Less than 12 months, Number of Issues	1	0
Less than 12 months, Fair Value	223	0
Less than 12 months, Gross Unrealized Depreciation	55	0
12 months or longer, Number of Issues	0	4
12 months or longer, Fair Value	0	215
12 months or longer, Gross Unrealized Depreciation	0	128
Total, Fair Value	223	215
Total, Gross Unrealized Depreciation	55	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	1	2
12 months or longer, Fair Value	701	1,170
12 months or longer, Gross Unrealized Depreciation	6	61
Total, Fair Value	701	4,663
Total, Gross Unrealized Depreciation	$ 6	$ 177