Acquisition of Maybrooke - Summary of Pro Forma Results (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Combinations [Abstract]
Pro forma revenues	$ 439.2	$ 466.0	$ 1,332.4	$ 1,340.5
Pro forma net (loss) income	$ (63.4)	$ 56.2	$ 29.8	$ 132.9
Pro forma net (loss) income per share - basic	$ (2.11)	$ 1.87	$ 0.99	$ 4.40
Pro forma net (loss) income per share - diluted	$ (2.11)	$ 1.83	$ 0.96	$ 4.30

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)-(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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