Income Taxes - Schedule Of Gross Unrecognized Income Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Beginning balance	$ 92.4	$ 75.5	$ 74.0
Increases related to tax positions taken during the current year	29.9	28.9	22.3
Increases related to tax positions taken during a prior year	0.0	0.3	0.0
Decreases related to tax positions taken during a prior year	(0.5)	0.0	0.0
Decreases related to settlements with tax authorities	0.0	(11.4)	(19.1)
Decreases related to expiration of statute of limitations	(15.8)	(0.9)	(1.7)
Ending balance	$ 106.0	$ 92.4	$ 75.5

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

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=SL6600010-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Unrecognized Tax Benefit
-URI http://asc.fasb.org/extlink&oid=6527854

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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