Earnings Per Share (Tables)

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

Schedule of Weighted Average Number of Shares

Our calculation of diluted earnings per share of common stock assumes that any shares of common stock outstanding were increased by shares that would be issued upon exercise of those stock units for which the average market price for the period exceeds the exercise price less the shares that could have been purchased by the Company with the related proceeds, including compensation expense measured but not yet recognized.

	Three Months Ended March 31,
(in millions)	2018	2017
Weighted-average number of shares of common stock outstanding - basic	106.8	108.3
Stock options	1.2	1.5
Restricted stock units	2.0	2.6
Adjusted weighted-average shares and assumed conversions — diluted	110.0	112.4