Share Plans (Tables)

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [Abstract]

Share-based Compensation Expense

Total share-based compensation expense for the three and six months ended June 30, 2019 and 2018 was as follows:

	Three months ended				Six months ended
In millions	June 30, 2019		June 30, 2018		June 30, 2019		June 30, 2018
Restricted stock units	$	2.9	$	1.9	$	5.7	$	4.3
Stock options	1.1		1.0		2.5		2.2
Performance share units	1.3		2.4		2.5		4.8
Total share-based compensation expense	$	5.3	$	5.3	$	10.7	$	11.3

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

We estimated the fair value of each stock option award issued in the annual share-based compensation grant using a Black-Scholes option pricing model, modified for dividends and using the following assumptions:

	2019 Annual Grant
Risk-free interest rate	2.89	%
Expected dividend yield	1.78	%
Expected share price volatility	23.3	%
Expected term (years)	6.1