Income Taxes - Income (Loss) Before Income Taxes (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Line Items]
Foreign	$ 149.7	$ 127.0	$ 7.7
Income (loss) before income taxes	1,199.8	673.9	(254.0)
Canada [Member]
Income Tax [Line Items]
Foreign	$ 1,050.1	$ 546.9	$ (261.7)

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.

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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