Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net income	$ 17,540	$ 12,786
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	6,681	6,336
Share-based compensation expense	5,478	3,603
Excess tax benefit from exercises of share-based arrangements	(5,661)	(1,581)
Changes in operating assets and liabilities, exclusive of effects of acquired companies:
Accounts receivable	(21,658)	(7,706)
Income tax payable	2,378	(190)
Prepaid expenses and other current assets	(2,596)	(262)
Accounts payable	671	(1,637)
Accrued liabilities	(1,601)	(2,152)
Deferred revenue	15,354	(772)
Net cash provided by operating activities	16,586	8,425
Cash flows from investing activities:
Proceeds from sale of investments	25	25
Cost of acquisitions, net of cash acquired	(181)	(15,175)
Additions to property and equipment	(13,839)	(4,334)
Decrease (increase) in other	295	(61)
Net cash used by investing activities	(13,700)	(19,545)
Cash flows from financing activities:
(Decrease) increase in net borrowings on revolving line of credit	(18,000)	5,000
Contributions from employee stock purchase plan	1,634	1,166
Proceeds from exercise of stock options	4,481	2,359
Excess tax benefits from exercises of share-based arrangements	5,661	1,581
Net cash (used) provided by financing activities	(6,224)	10,106
Net decrease in cash and cash equivalents	(3,338)	(1,014)
Cash and cash equivalents at beginning of period	6,406	1,326
Cash and cash equivalents at end of period	$ 3,068	$ 312