Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization expense for intangible assets	$ 2,008,000	$ 1,696,000	$ 4,014,033	$ 3,368,216
Database [Member]
Finite-Lived Intangible Assets [Line Items]
Amount capitalized to intangible asset	1,141,000	1,529,000	2,339,000	2,777,000
Amortization expense for intangible assets	1,085,000	917,000	2,135,000	1,789,000
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense for intangible assets	225,000	231,000	452,000	462,000
Website [Member]
Finite-Lived Intangible Assets [Line Items]
Amount capitalized to intangible asset	735,000	871,000	1,486,000	1,751,000
Amortization expense for intangible assets	$ 698,000	$ 548,000	$ 1,427,000	$ 1,118,000