Net (Loss) Earnings Per Common Share - Calculation of Basic and Diluted Net Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Numerator
Distributed and allocated undistributed net loss to non-vested restricted stockholders		$ 0.1	$ (0.7)
Net (loss) earnings available to common stockholders		(43.2)	102.4
Distributed and allocated undistributed net (loss) earnings to common stockholders		(43.1)	101.7
Distributed net (loss) earnings - dividends paid to common stockholders		(31.0)	(25.4)
Allocation of undistributed net (loss) earnings to common stockholders		$ (74.1)	$ 76.3
Denominator
Weighted average number of common shares outstanding - basic		193.4	195.2
Basic net earnings per common share:
Distributed net earnings to common stockholders		$ 0.16	$ 0.13
Allocated undistributed net (loss) earnings to common stockholders		(0.38)	0.38
Net (loss) earnings per common share – basic	[1]	$ (0.22)	$ 0.51
Numerator
Add: Allocated undistributed net earnings to unvested restricted stockholders			$ 0.6
Less: Undistributed net earnings (loss) reallocated to non-vested restricted stockholders			(0.6)
Distributed and allocated undistributed net (loss) earnings to common stockholders		$ (43.1)	101.7
Net (loss) earnings available to common stockholders – diluted		$ (43.1)	$ 101.7
Denominator
Weighted average number of common shares outstanding - basic		193.4	195.2
Effect of contingently issuable shares		0.8	0.7
Effect of unvested restricted stock units		0.9	0.9
Weighted average number of common shares outstanding - diluted under two-class		195.1	196.8
Effect of unvested restricted stock - participating security		0.6	0.7
Weighted average number of common shares outstanding - diluted under treasury stock	[1]	195.7	197.5
Diluted net (loss) earnings per common share(1)	[1]	$ (0.22)	$ 0.51

[1] The Company early adopted ASU 2016-09 on a prospective basis, related to the recognition of excess tax benefits to the income statement which were previously recorded in additional paid-in capital, effective January 1, 2016. This resulted in an additional 404,347 diluted weighted average number of common shares outstanding for the three months ended March 31, 2016, and recognition of excess tax benefits of $9.6 million in net earnings from continuing operations, and $1.0 million in net earnings from discontinued operations for the three months ended March 31, 2016. As a result, continuing operations net earnings per common share increased by $0.05 per share for the three months ended March 31, 2016. Refer to Note 2, “Recently Issued Accounting Standards” of the Notes to Condensed Consolidated Financial Statements for further details.