Lease Obligations (Schedule of Future Lease Commitments) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Capital Leases
Future minimum lease commitments, 2018	$ 69.5
Future minimum lease commitments, 2019	49.4
Future minimum lease commitments, 2020	39.4
Future minimum lease commitments, 2021	29.0
Future minimum lease commitments, 2022	9.1
Future minimum lease commitments, thereafter	0.0
Total minimum lease payments	196.4
Less amounts representing interest	(15.2)
Total capital lease obligations, net of interest	181.2	$ 98.6
Less current portion	(63.5)
Long-term portion of capital lease obligations, net of interest	117.7
Operating Leases
Future minimum lease commitments, 2018	90.7
Future minimum lease commitments, 2019	57.3
Future minimum lease commitments, 2020	33.9
Future minimum lease commitments, 2021	19.2
Future minimum lease commitments, 2022	12.3
Future minimum lease commitments, thereafter	30.3
Total minimum lease payments	$ 243.7