Investments - Real Estate Transactions (Details) - Certain real estate joint ventures $ in Millions	1 Months Ended
Sep. 30, 2017 USD ($)
Real Estate Transactions
Net pre-tax realized capital gain	$ 690.9
Net after-tax realized capital gain	410.8
Real estate
Real Estate Transactions
Net increase, assets	293.4
Other investments
Real Estate Transactions
Net increase, assets	222.4
Cash and cash equivalents
Real Estate Transactions
Net increase, assets	219.6
Long-term debt
Real Estate Transactions
Net increase, liabilities	49.4
Income taxes currently payable
Real Estate Transactions
Net increase, liabilities	179.1
Deferred income taxes
Real Estate Transactions
Net increase, liabilities	$ 101.0

Net increase (decrease) in assets resulting from exchange agreement to exit real estate joint ventures, which resulted in the entity transferring interest in certain real estate properties in exchange for the joint venture partner's interest in certain other real estate properties, and subsequent sales of real estate properties.

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Net increase (decrease) in liabilities resulting from exchange agreement to exit real estate joint ventures, which resulted in the entity transferring interest in certain real estate properties in exchange for the joint venture partner's interest in certain other real estate properties, and subsequent sales of real estate properties.

+ References

No definition available.

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The net realized gains or losses on investments during the period, net of tax, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

+ References

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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

+ 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 210.7-04.3(a))
-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 325
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=75031664&loc=d3e22529-158502

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