Property and Equipment - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Property Plant And Equipment [Abstract]
Depreciation expense	$ 10.4	$ 9.1
Non-cash increases property and equipment acquired under capital leases	0.5	0.4
Non-cash increases property and equipment purchases in accounts payable and accrued liabilities	$ 0.8	$ 1.5