Intangible Assets - Summary of Identified Intangible Assets (Detail) - USD ($)	Mar. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ (40,116,778)	$ (38,738,292)
Intangible assets, net	16,297,789	15,686,954
Database [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	24,121,000	22,790,000
Accumulated amortization	(17,733,000)	(17,121,000)
Intangible assets, net	6,388,000	5,669,000
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	14,100,000	14,100,000
Accumulated amortization	(8,563,000)	(8,328,000)
Intangible assets, net	5,537,000	5,772,000
Website [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	15,393,000	14,735,000
Accumulated amortization	(11,125,000)	(10,669,000)
Intangible assets, net	4,268,000	4,066,000
Acquired Below Market Lease [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	2,800,000	2,800,000
Accumulated amortization	(2,695,000)	(2,620,000)
Intangible assets, net	$ 105,000	$ 180,000