Investments (Available-For-Sale Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
U.S. Treasury obligations [Member]
Fixed maturities, available for sale
Amortized Cost	$ 122,855	$ 163,714
Gross Unrealized Gains	1,696	3,785
Gross Unrealized Losses	659	987
Estimated Fair Value	123,892	166,512
U.S. Government-sponsored enterprise obligations [Member]
Fixed maturities, available for sale
Amortized Cost	25,456	38,022
Gross Unrealized Gains	927	1,641
Gross Unrealized Losses	49	100
Estimated Fair Value	26,334	39,563
State and municipal bonds [Member]
Fixed maturities, available for sale
Amortized Cost	904,719	1,015,555
Gross Unrealized Gains	36,739	47,395
Gross Unrealized Losses	823	335
Estimated Fair Value	940,635	1,062,615
Corporate debt [Member]
Fixed maturities, available for sale
Amortized Cost	1,296,128	1,389,970
Gross Unrealized Gains	24,720	44,234
Gross Unrealized Losses	29,162	17,103
Estimated Fair Value	1,291,686	1,417,101
Residential mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	233,659	266,306
Gross Unrealized Gains	6,039	10,198
Gross Unrealized Losses	1,311	448
Estimated Fair Value	238,387	276,056
Agency commercial mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	10,851	15,344
Gross Unrealized Gains	174	208
Gross Unrealized Losses	26	59
Estimated Fair Value	10,999	15,493
Other commercial mortgage-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	29,983	50,025
Gross Unrealized Gains	354	1,137
Gross Unrealized Losses	203	99
Estimated Fair Value	30,134	51,063
Other asset-backed securities [Member]
Fixed maturities, available for sale
Amortized Cost	98,412	116,541
Gross Unrealized Gains	54	288
Gross Unrealized Losses	246	205
Estimated Fair Value	98,220	116,624
Debt Securities [Member]
Fixed maturities, available for sale
Amortized Cost	2,722,063	3,055,477
Gross Unrealized Gains	70,703	108,886
Gross Unrealized Losses	32,479	19,336
Estimated Fair Value	$ 2,760,287	$ 3,145,027

Available for Sale securities debt securities.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

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-Publisher FASB
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-Topic 320
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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