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Income Taxes - Changes in Valuation Allowance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance, valuation allowance	$ 552.5	$ 607.8	$ 839.1
Remeasurement of deferred tax assets	(41.6)	(32.1)	(205.2)
Release of valuation allowance	0.0	0.0	0.0
Expiration of net operating losses	(10.8)	(12.3)	0.0
Other change in valuation allowance	$ (7.7)	(11.0)	(26.1)
Balance, valuation allowance		$ 552.5	$ 607.8

X

- Definition

Valuation Allowance, Deferred Tax Asset, Expiration of Net Operating Losses

+ References

No definition available.

+ Details

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X

- Definition

Valuation Allowance, Deferred Tax Asset, Release of Valuation Allowance

+ References

No definition available.

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X

- Definition

Valuation Allowance, Deferred Tax Asset, Remeasurement Due To Tax Cuts & Jobs Act

+ References

No definition available.

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X

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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X

- Definition

Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=116821951&loc=d3e32123-109318

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X

- Definition

Amount of valuation and qualifying accounts and reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

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