Income Taxes - Unrecognized Tax Benefits and Effect on Effective Income Tax Rate (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Beginning balance of unrecognized tax benefits	$ 239.1	$ 188.9	$ 221.9
Additions for tax positions of current year	13.4	3.1	5.2
Additions for tax positions of prior years	23.3	111.9	7.7
Reductions for tax positions of prior years	(23.0)	(7.2)	(39.8)
Reductions for lapses of statutes of limitation	(40.7)	(57.6)	(6.2)
Ending balance of unrecognized tax benefits	$ 212.1	$ 239.1	$ 188.9

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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 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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