Post Retirement Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Components of net periodic benefit costs:
Service cost	$ 8.1	$ 8.2	$ 6.4
Interest cost	0.5	1.1	2.6
Expected return on plan assets	(1.8)	(2.5)	(2.0)
Settlement loss recognized	0.1
Amortization of prior service (credit) cost	0.9	1.2	1.1
Amortization of actuarial (gains) losses	2.6	3.5	0.9
Net periodic benefit costs	$ 10.4	$ 11.5	$ 9.0