Share-based compensation (Tables)

6 Months Ended

Jun. 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)	June 30, 2020
	PSUs - IPO Incentive Awards		PSUs - 2019 Long Term Incentive (LTI)		RSUs		Stock Options		2018 Long Term Incentive Plan (LTIP)
Unrecognized compensation cost related to unvested awards	$	2.1	$	1.0	$	8.0	$	1.6	$	0.2
Weighted average recognition period (years)	1.5 years		1.5 years		1.5 years		1.7 years		0.5 years

Summary of outstanding share-settled awards

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

	Number of Shares
Three months ended June 30, 2020	PSUs - IPO Incentive Awards	PSUs - 2019 LTI	RSUs	Stock Options	2018 Long Term Incentive Plan (LTIP)
Unvested, beginning of period	543,196	382,327	1,320,837	1,374,945	856,099
Granted	—	—	—	—	—
Vested	—	—	—	—	—
Forfeited	—	4,824	46,085	—	9,942
Unvested, end of period	543,196	377,503	1,274,752	1,374,945	846,157