Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income	$ 12,786	$ 11,352
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	6,336	5,219
Share-based compensation expense	3,603	2,969
Excess tax benefit from exercises of share-based arrangements	(1,581)	(1,692)
Changes in operating assets and liabilities, exclusive of effects of acquired companies:
Accounts receivable	(7,706)	(8,026)
Income tax payable	(190)	1,552
Prepaid expenses and other current assets	(262)	(814)
Accounts payable	(1,637)	(295)
Accrued liabilities	(2,152)	1,197
Deferred revenue	(772)	7,865
Net cash provided by operating activities	8,425	19,327
Cash flows from investing activities:
Proceeds from sale of investments	25	25
Cost of acquisitions, net of cash acquired	(15,175)
Additions to property and equipment	(4,334)	(8,416)
(Increase) decrease in other	(61)	214
Net cash used by investing activities	(19,545)	(8,177)
Cash flows from financing activities:
Increase in net borrowings on revolving line of credit	5,000	5,000
Purchase of treasury shares		(20,884)
Contributions from employee stock purchase plan	1,166	924
Proceeds from exercise of stock options	2,359	1,416
Excess tax benefits from exercises of share-based arrangements	1,581	1,692
Net cash provided (used) by financing activities	10,106	(11,852)
Net decrease in cash and cash equivalents	(1,014)	(702)
Cash and cash equivalents at beginning of period	1,326	2,114
Cash and cash equivalents at end of period	$ 312	$ 1,412