CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Cash flows from operating activities:
Net income	$ 11,883	$ 8,493
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	3,656	3,322
Share-based compensation expense	3,462	2,575
Excess tax benefit from exercises of share-based arrangements	(2,158)	(1,523)
Changes in operating assets and liabilities
Accounts receivable	24,298	22,558
Income tax receivable	7,695	5,638
Prepaid expenses and other current assets	(1,547)	(1,204)
Accounts payable	39	(579)
Accrued liabilities	(13,328)	(7,031)
Deferred revenue	(17,440)	(15,165)
Net cash provided by operating activities	16,560	17,084
Cash flows from investing activities:
Proceeds from sale of investments	8	25
Additions to property and equipment	(3,630)	(5,089)
Decrease in other	300	239
Net cash used by investing activities	(3,322)	(4,825)
Cash flows from financing activities:
Decrease in net borrowings on revolving line of credit		(18,000)
Contributions from employee stock purchase plan	849	670
Proceeds from exercise of stock options	2,024	1,637
Excess tax benefit from exercises of share-based arrangements	2,158	1,523
Net cash provided (used) by financing activities	5,031	(14,170)
Net increase (decrease) in cash and cash equivalents	18,269	(1,911)
Cash and cash equivalents at beginning of period	78,876	6,406
Cash and cash equivalents at end of period	$ 97,145	$ 4,495