CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities:
Net income	$ 22,942,482	$ 18,363,047	$ 13,945,993
Adjustments to reconcile net income to net cash provided by operating activities, excluding the effects of acquisition:
Amortization of acquisition-related intangible assets	323,076	323,076	4,130,256
Depreciation & amortization	4,575,412	4,353,748	4,035,410
Stock-based compensation expense	4,509,727	4,029,022	3,008,567
Deferred income taxes	788,258	(187,132)	3,493,455
Nonrecurring gain on acquisition of business, net of tax			(2,184,255)
(Gain) loss on disposal of property and equipment	37,857	12,690	(2,872)
Changes in operating assets and liabilities:
(Increase) in trade accounts receivable, net	(7,246,782)	(3,095,308)	(1,467,177)
(Increase) decrease in prepaid expenses & other current assets	1,308,384	(1,664,493)	1,746,076
(Increase) in other assets	(358)	(1,122)	(96,977)
Increase (decrease) in accounts payable	3,439,367	(1,273,509)	1,080,857
Increase (decrease) in accrued expenses	(92,038)	357,945	3,565,705
Increase (decrease) in other current liabilities	(265,026)	29,742	(447,608)
Increase (decrease) in other long-term liabilities	282,254	742,975	(286,707)
Net cash provided by operating activities	30,602,613	21,990,681	30,520,723
Cash flows from investing activities:
Purchases of property and equipment	(6,136,666)	(4,102,176)	(3,355,011)
Proceeds from sale of property and equipment	7,711	3,813	18,403
Capitalized internal use software development costs	(450,770)	(469,602)	(509,986)
Acquisition of business			(1,500,000)
Net cash used in investing activities	(6,579,725)	(4,567,965)	(5,346,594)
Cash flows from financing activities:
Cash dividends on common stock		(35,501,457)	(19,149,970)
Cash restricted for payment of dividend	(16,230,966)
Proceeds from employee common stock purchases	651,600	679,277	465,086
Proceeds from exercise of employee stock options		72,769	206,223
Tax deductions related to stock-based compensation	1,509,039	381,315	1,564,480
Net cash used in financing activities	(14,070,327)	(34,368,096)	(16,914,181)
Net increase (decrease) in cash and cash equivalents	9,952,561	(16,945,380)	8,259,948
Cash and cash equivalents, beginning of period	51,686,503	68,631,883	60,371,935
Cash and cash equivalents, end of period	61,639,064	51,686,503	68,631,883
Other cash flow information:
Income taxes paid	$ 11,726,661	$ 12,189,184	$ 1,359,193