Intangible Assets (Details) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Identified intangible assets including amounts of accumulated amortization
Accumulated amortization	$ (22,971,153)	$ (19,437,856)
Intangible assets, net	16,523,634	17,155,195
Database [Member]
Identified intangible assets including amounts of accumulated amortization
Intangible assets, gross	14,682,000	13,223,000
Accumulated amortization	(11,339,000)	(9,784,000)
Intangible assets, net	3,343,000	3,439,000
Customer relationships [Member]
Identified intangible assets including amounts of accumulated amortization
Intangible assets, gross	14,100,000	14,100,000
Accumulated amortization	(5,200,000)	(4,462,000)
Intangible assets, net	8,900,000	9,638,000
Web site [Member]
Identified intangible assets including amounts of accumulated amortization
Intangible assets, gross	7,913,000	6,470,000
Accumulated amortization	(4,797,000)	(3,784,000)
Intangible assets, net	3,116,000	2,686,000
Acquired below market lease [Member]
Identified intangible assets including amounts of accumulated amortization
Intangible assets, gross	2,800,000	2,800,000
Accumulated amortization	(1,635,000)	(1,408,000)
Intangible assets, net	$ 1,165,000	$ 1,392,000