Share-Based Compensation Plans - Schedule of Compensation Costs by Value Driver Award Programs (Details) - Value Driver Award - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
2016 Value Driver Award Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 0.0	$ 0.0	$ 7.0
2017 Value Driver Performance Share Unit Award Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	0.0	0.1	10.3
2018 EQT Value Driver Performance Share Unit Award Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	0.1	3.3	0.0
2019 EQT Value Driver Performance Share Unit Award Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 2.4	$ 0.0	$ 0.0