Leases and commitments - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash paid for amounts included in the measurement of lease liabilities:
Cash payments for operating leases included in operating activities	$ 44.9	$ 41.6
Cash payments for finance leases included in financing activities	1.9	1.8
Cash payments for finance lease included in operating activities	0.1	0.2
Right-of-use assets obtained in exchange for lease obligations:
Operating leases	$ 20.4	$ 40.9