CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from operating activities:
Net income	$ 36,109	$ 26,623
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	7,484	7,281
Share-based compensation expense	8,861	7,002
Excess tax benefit from exercises of share-based arrangements	(8,827)	(3,206)
Changes in operating assets and liabilities, exclusive of effects of acquired companies:
Accounts receivable	(36,624)	(38,203)
Income taxes	2,735	7,746
Prepaid expenses and other current assets	(549)	(2,069)
Accounts payable	(371)	51
Accrued liabilities	(5,685)	(4,237)
Deferred revenue	11,680	27,840
Net cash provided by operating activities	14,813	28,828
Cash flows from investing activities:
Purchase of cost method investment	(15,000)
Purchase of held-to-maturity securities	(6,449)
Cost of acquisitions, net of cash acquired	(6,447)
Additions to property and equipment	(6,126)	(6,477)
(Increase) decrease in other	(9)	343
Net cash used by investing activities	(34,031)	(6,134)
Cash flows from financing activities:
Purchase of treasury shares	(645)	(22,815)
Proceeds from exercise of stock options	6,729	4,117
Contributions from employee stock purchase plan	2,243	2,014
Excess tax benefit from exercises of share-based arrangements	8,827	3,206
Net cash provided (used) by financing activities	17,154	(13,478)
Net (decrease) increase in cash and cash equivalents	(2,064)	9,216
Cash and cash equivalents at beginning of period	206,167	78,876
Cash and cash equivalents at end of period	$ 204,103	$ 88,092