Securities in an Unrealized Loss Position (Securities in an Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Less Than 12 Months, Fair Value	$ 2,024,847	$ 3,085,977
Available-for-sale Securities, Less Than 12 Months, Gross Unrealized Losses	20,681	84,259
Available-for-sale Securities, 12 Months or Greater, Fair Value	870,357	355,098
Available-for-sale Securities, 12 Months or Greater, Gross Unrealized Losses	48,461	33,194
Available-for-sale Securities, Fair Value	2,895,204	3,441,075
Available For Sale Securities, Gross Unrealized Losses	69,142	117,453
U.S. government and government agency
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Less Than 12 Months, Fair Value	84,750	260,882
Available-for-sale Securities, Less Than 12 Months, Gross Unrealized Losses	522	7,927
Available-for-sale Securities, 12 Months or Greater, Fair Value	84,850	2,163
Available-for-sale Securities, 12 Months or Greater, Gross Unrealized Losses	2,635	55
Available-for-sale Securities, Fair Value	169,600	263,045
Available For Sale Securities, Gross Unrealized Losses	3,157	7,982
State and municipal
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Less Than 12 Months, Fair Value	158,594	899,613
Available-for-sale Securities, Less Than 12 Months, Gross Unrealized Losses	631	24,503
Available-for-sale Securities, 12 Months or Greater, Fair Value	150,284	87,345
Available-for-sale Securities, 12 Months or Greater, Gross Unrealized Losses	3,389	5,334
Available-for-sale Securities, Fair Value	308,878	986,958
Available For Sale Securities, Gross Unrealized Losses	4,020	29,837
Mortgage-backed securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Less Than 12 Months, Fair Value	75,739	578,603
Available-for-sale Securities, Less Than 12 Months, Gross Unrealized Losses	332	17,964
Available-for-sale Securities, 12 Months or Greater, Fair Value	312,922	140,648
Available-for-sale Securities, 12 Months or Greater, Gross Unrealized Losses	9,169	8,965
Available-for-sale Securities, Fair Value	388,661	719,251
Available For Sale Securities, Gross Unrealized Losses	9,501	26,929
Corporate
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Less Than 12 Months, Fair Value	1,586,238	1,013,373
Available-for-sale Securities, Less Than 12 Months, Gross Unrealized Losses	8,697	17,066
Available-for-sale Securities, 12 Months or Greater, Fair Value	214,628	105,074
Available-for-sale Securities, 12 Months or Greater, Gross Unrealized Losses	16,084	13,034
Available-for-sale Securities, Fair Value	1,800,866	1,118,447
Available For Sale Securities, Gross Unrealized Losses	24,781	30,100
Foreign government
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Less Than 12 Months, Fair Value	76,471	320,215
Available-for-sale Securities, Less Than 12 Months, Gross Unrealized Losses	3,907	16,286
Available-for-sale Securities, 12 Months or Greater, Fair Value	85,025	0
Available-for-sale Securities, 12 Months or Greater, Gross Unrealized Losses	14,158	0
Available-for-sale Securities, Fair Value	161,496	320,215
Available For Sale Securities, Gross Unrealized Losses	18,065	16,286
Fixed maturity securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Less Than 12 Months, Fair Value	1,981,792	3,072,686
Available-for-sale Securities, Less Than 12 Months, Gross Unrealized Losses	14,089	83,746
Available-for-sale Securities, 12 Months or Greater, Fair Value	847,709	335,230
Available-for-sale Securities, 12 Months or Greater, Gross Unrealized Losses	45,435	27,388
Available-for-sale Securities, Fair Value	2,829,501	3,407,916
Available For Sale Securities, Gross Unrealized Losses	59,524	111,134
Common stocks
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Less Than 12 Months, Fair Value	15,929	0
Available-for-sale Securities, Less Than 12 Months, Gross Unrealized Losses	5,453	0
Available-for-sale Securities, 12 Months or Greater, Fair Value	0	0
Available-for-sale Securities, 12 Months or Greater, Gross Unrealized Losses	0	0
Available-for-sale Securities, Fair Value	15,929	0
Available For Sale Securities, Gross Unrealized Losses	5,453	0
Preferred stocks
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Less Than 12 Months, Fair Value	27,126	13,291
Available-for-sale Securities, Less Than 12 Months, Gross Unrealized Losses	1,139	513
Available-for-sale Securities, 12 Months or Greater, Fair Value	22,648	19,868
Available-for-sale Securities, 12 Months or Greater, Gross Unrealized Losses	3,026	5,806
Available-for-sale Securities, Fair Value	49,774	33,159
Available For Sale Securities, Gross Unrealized Losses	4,165	6,319
Equity securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Less Than 12 Months, Fair Value	43,055	13,291
Available-for-sale Securities, Less Than 12 Months, Gross Unrealized Losses	6,592	513
Available-for-sale Securities, 12 Months or Greater, Fair Value	22,648	19,868
Available-for-sale Securities, 12 Months or Greater, Gross Unrealized Losses	3,026	5,806
Available-for-sale Securities, Fair Value	65,703	33,159
Available For Sale Securities, Gross Unrealized Losses	$ 9,618	$ 6,319

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This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 6

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563

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- Definition

This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 6

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563

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- Definition

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- Definition

Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses Accumulated In AOCI

+ References

No definition available.

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- Definition

Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI

+ References

No definition available.

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- Definition

Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses Accumulated In AOCI

+ References

No definition available.

+ Details

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