Business Combinations and Other Investments - Acquisition of HealthMEDX - Additional Information (Detail) - USD ($)	Oct. 27, 2016	Oct. 14, 2016	Dec. 31, 2017
Business Acquisition [Line Items]
Date of acquisition		Oct. 14, 2016
HealthMEDX, LLC [Member]
Business Acquisition [Line Items]
Date of acquisition	Oct. 27, 2016
Business combination, aggregate consideration	$ 39,183,000
Business combination, estimated consideration payable	$ 3,500,000
Outstanding contingent consideration			$ 900,000