Leases - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Leases [Line Items]
Pump equipment	$ 13.9	$ 11.2
Accumulated depreciation related to leased assets	3.9	2.4
Depreciation expense for medical equipment	6.3	$ 4.8
Operating lease rental expenses	$ 1.0
Capital Leases [Member]
Leases [Line Items]
Weighted average interest rate under capital leases	5.10%