Share Plans (Tables)

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Share-based Compensation Expense

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

	Three months ended				Nine months ended
In millions	September 30, 2019		September 30, 2018		September 30, 2019		September 30, 2018
Restricted stock units	$	2.5	$	2.4	$	8.2	$	6.7
Stock options	0.9		1.3		3.4		3.5
Performance share units	1.2		1.4		3.7		6.2
Total share-based compensation expense	$	4.6	$	5.1	$	15.3	$	16.4

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