Effects of Restatement on Reportable Segments (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total segment operating profit		$ 178.4	$ 234.8
Income before income taxes	[1]	36.6	166.5
Net interest expense		(82.1)	(13.3)
Operating segments | Onshore/Offshore
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total segment operating profit		142.8	38.4
Corporate items
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Corporate income (expense)	[2]	(59.7)	(55.0)
Net interest expense		(82.1)	(13.3)
Total corporate items		(141.8)	(68.3)
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total segment operating profit		175.5	254.9
Income before income taxes		298.0	194.8
Net interest expense		(81.7)
Previously Reported | Operating segments | Onshore/Offshore
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total segment operating profit		139.9	58.5
Previously Reported | Corporate items
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Corporate income (expense)		204.2	(46.8)
Net interest expense		(81.7)
Total corporate items		122.5	(60.1)
Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total segment operating profit		2.9	(20.1)
Income before income taxes		(261.4)	(28.3)
Net interest expense		(0.4)
Restatement Adjustment | Operating segments | Onshore/Offshore
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total segment operating profit		2.9	(20.1)
Restatement Adjustment | Corporate items
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Corporate income (expense)		(263.9)	(8.2)
Net interest expense		(0.4)
Total corporate items		$ (264.3)	$ (8.2)

[1] Includes amounts attributable to noncontrolling interests.

[2] Corporate expense primarily includes corporate staff expenses, stock-based compensation expenses, other employee benefits, certain foreign exchange gains and losses, and merger-related transaction expenses.