Intangible Assets - Summary of Identified Intangible Assets (Detail) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ (45,229,777)	$ (41,861,561)
Intangible assets, net	19,081,875	17,922,282
Database [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	30,923,000	28,146,000
Accumulated amortization	(21,763,000)	(19,974,000)
Intangible assets, net	9,160,000	8,172,000
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	14,100,000	14,100,000
Accumulated amortization	(9,725,000)	(9,263,000)
Intangible assets, net	4,375,000	4,837,000
Website [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	19,289,000	17,538,000
Accumulated amortization	(13,742,000)	(12,624,000)
Intangible assets, net	$ 5,547,000	$ 4,914,000