Investments (Net Investment Income) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Investment Income [Line Items]
Gross investment income	$ 439,314	$ 423,737	$ 438,375
Less: investment expenses	(22,727)	(19,719)	(19,364)
Net investment income	416,587	404,018	419,011
Fixed maturities, available-for-sale
Net Investment Income [Line Items]
Gross investment income	269,073	262,532	278,747
Equity securities, available-for-sale
Net Investment Income [Line Items]
Gross investment income	2	2	1
Trading account assets
Net Investment Income [Line Items]
Gross investment income	2,800	1,018	657
Commercial mortgage and other loans
Net Investment Income [Line Items]
Gross investment income	86,354	81,848	84,006
Policy loans
Net Investment Income [Line Items]
Gross investment income	62,304	60,847	59,287
Short-term investments and cash equivalents
Net Investment Income [Line Items]
Gross investment income	1,042	528	654
Other long-term investments
Net Investment Income [Line Items]
Gross investment income	$ 17,739	$ 16,962	$ 15,023

Amount before accretion (amortization) of purchase discount (premium) of interest income and dividend income on nonoperating securities.

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Amount of expenses related to the generation of investment income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.2)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.2)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 16
-Article 12

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+ References

No definition available.

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