Property and Equipment (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and Equipment (Textual) [Abstract]
Depreciation expense	$ 98.9	$ 92.8	$ 85.9
Assets under capital leases	17.1	17.1
Accumulated amortization related to capital leases	12.2	11.2
Depreciation expense related to capital leases	$ 1.0	$ 1.0	$ 1.0