Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 8,493	$ 5,681
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	3,322	3,026
Share-based compensation expense	2,575	1,835
Excess tax benefit from exercises of share-based arrangements	(1,523)	(686)
Changes in operating assets and liabilities, exclusive of effects of acquired companies:
Accounts receivable	22,558	32,037
Income tax payable	5,638	2,267
Prepaid expenses and other current assets	(1,204)	(341)
Accounts payable	(579)	(629)
Accrued liabilities	(7,031)	(9,379)
Deferred revenue	(15,165)	(15,727)
Net cash provided by operating activities	17,084	18,084
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	(5,089)	(1,048)
Decrease in other	239
Net cash used by investing activities	(4,825)	(6,897)
Cash flows from financing activities:
Decrease in net borrowings on revolving line of credit	(18,000)	(4,700)
Contributions from employee stock purchase plan	670	509
Proceeds from exercise of stock options	1,637	924
Excess tax benefits from exercises of share-based arrangements	1,523	686
Net cash used by financing activities	(14,170)	(2,581)
Net (decrease) increase in cash and cash equivalents	(1,911)	8,606
Cash and cash equivalents at beginning of period	6,406	1,326
Cash and cash equivalents at end of period	$ 4,495	$ 9,932