Reclassifications from Accumulated Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income Reclassification (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Available for sale securities:
Income from operations before income tax	$ 34.4	$ 99.3
General, administrative and corporate expenses	121.0	121.3
Income tax expense	(3.6)	(2.8)
Net income	30.8	96.5
Reclassification out of AOCI
Available for sale securities:
Net income	1.4	1.0
Reclassification out of AOCI \| Available for sale securities
Available for sale securities:
Realized gains on sale of securities	2.0	2.3
Realized (losses) on sale of securities	(1.9)	(1.3)
Income from operations before income tax	0.1	1.0
Income tax expense	(0.1)	(0.2)
Net income	0.0	0.8
Reclassification out of AOCI \| Realized derivatives
Available for sale securities:
General, administrative and corporate expenses	1.7	0.3
Income tax expense	(0.3)	(0.1)
Net income	$ 1.4	$ 0.2

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This item represents the gross profit realized on the sale of debt or equity securities 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 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

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This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(1)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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Amount, before tax, of income (loss) including portion attributable to noncontrolling interest. Includes, but is not limited to, income (loss) from continuing operations, discontinued operations and equity method investments.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a),(b)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

+ 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 210.5-03.4)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 30
-Paragraph 8
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