Property and Equipment - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Property Plant And Equipment [Abstract]
Depreciation expense	$ 13.3	$ 12.5	$ 35.9	$ 32.9
Property and equipment acquired under capital leases, increased amount			2.9	1.1
Property and equipment purchased through accounts payable and accrued liabilities, increased amount			$ 4.4	$ 0.8