Property and Equipment - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Property Plant And Equipment [Abstract]
Depreciation expense	$ 12.3	$ 11.3	$ 22.6	$ 20.4
Property and equipment acquired under capital leases, increased amount			2.1	0.8
Property and equipment purchased through accounts payable and accrued liabilities, increased amount			$ 0.1	$ 2.0