Condensed Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities:
Net income	$ 5,681	$ 5,728
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	3,026	2,585
Share-based compensation expense	1,835	1,449
Excess tax benefit from exercises of share-based arrangements	(686)	(272)
Changes in operating assets and liabilities, exclusive of effects of acquired companies:
Accounts receivable	32,037	15,214
Income tax payable	2,267	3,592
Prepaid expenses and other current assets	(341)	(343)
Accounts payable	(629)	(180)
Accrued liabilities	(9,379)	492
Deferred revenue	(15,727)	(10,798)
Net cash provided by operating activities	18,084	17,467
Cash flows from investing activities:
Proceeds from sale of investments	25	25
Cost of acquisitions, net of cash acquired	(5,874)
Additions to property and equipment	(1,048)	(7,804)
Decrease in other		214
Net cash used by investing activities	(6,897)	(7,565)
Cash flows from financing activities:
Purchase of treasury shares		(6,839)
Decrease in net borrowings on revolving line of credit	(4,700)	(4,000)
Contributions from employee stock purchase plan	509	456
Proceeds from exercise of stock options	924	343
Excess tax benefits from exercises of share-based arrangements	686	272
Net cash used by financing activities	(2,581)	(9,768)
Net increase in cash and cash equivalents	8,606	134
Cash and cash equivalents at beginning of year	1,326	2,114
Cash and cash equivalents at end of year	$ 9,932	$ 2,248