Share-based compensation (Tables)

9 Months Ended

Sep. 30, 2020

Share-based Payment Arrangement [Abstract]

Summary of unrecognized compensation cost associated with unvested awards and weighted average period over which it is expected to be recognized

The following tables present unrecognized compensation cost associated with unvested awards and weighted average period over which it is expected to be recognized:

(Millions)	September 30, 2020
	RSUs		Stock Options
Unrecognized compensation cost related to unvested awards	$	6.4	$	1.3
Weighted average recognition period (years)	1.3 years		1.5 years

Summary of outstanding share-settled awards

The following table summarizes outstanding and changes in share-settled awards for the three and nine months ended September 30, 2020:

	Number of Shares
Three months ended September 30, 2020	RSUs	Stock Options
Unvested, beginning of period	1,274,752	1,374,945
Granted	—	—
Vested	—	—
Forfeited	1,060	—
Unvested, end of period	1,273,692	1,374,945

	Number of Shares
Nine months ended September 30, 2020	RSUs	Stock Options
Unvested, beginning of period	1,353,852	1,374,945
Granted	—	—
Vested	—	—
Forfeited	80,160	—
Unvested, end of period	1,273,692	1,374,945