Amount, before 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.

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+ 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=63488584&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 FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-16(Column G))
-URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574960-122915

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+ References

No definition available.

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Investments (Components of Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Investment Income [Line Items]
Investment income, gross									$ 2,006,621	$ 1,861,392	$ 1,704,201
Less investment expenses									(14,624)	(11,520)	(12,009)
Net investment income	$ 512,709	$ 500,202	$ 493,489	$ 485,597	$ 475,633	$ 463,583	$ 459,830	$ 450,826	1,991,997	1,849,872	1,692,192
Fixed Maturity Securities [Member]
Net Investment Income [Line Items]
Investment income, gross									1,876,542	1,729,176	1,566,409
Equity Securities [Member]
Net Investment Income [Line Items]
Investment income, gross									764	531	441
Mortgage Loans on Real Estate [Member]
Net Investment Income [Line Items]
Investment income, gross									122,680	122,985	131,892
Cash and Cash Equivalents [Member]
Net Investment Income [Line Items]
Investment income, gross									2,562	3,201	601
Other [Member]
Net Investment Income [Line Items]
Investment income, gross									$ 4,073	$ 5,499	$ 4,858