Leasing - Assets and liabilities, lessee (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Assets
Operating lease assets	$ 159.1	$ 157.3
Finance lease assets	80.5	69.5
Total lease assets	239.6	226.8
Current liabilities:
Current portion of operating lease liabilities	45.3	47.4
Current portion of finance lease liabilities	22.9	20.9
Noncurrent liabilities:
Operating lease liabilities	121.6	114.5
Finance lease liabilities	59.5	50.3
Total lease liabilities	$ 249.3	$ 233.1