CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income	$ 27,348	$ 37,825
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	17,308	14,112
Share-based compensation expense	14,416	10,557
Deferred income tax benefit	(4,785)	(2,658)
Changes in operating assets and liabilities, exclusive of effects of acquired companies:
Accounts receivable	9,622	30,227
Income taxes	12,425	4,053
Prepaid expenses and other current assets	(3,064)	1,333
Accounts payable	(1,501)	(1,752)
Accrued liabilities	(4,665)	(17,952)
Deferred revenue	(43,147)	(31,114)
Net cash provided by operating activities	23,957	44,631
Cash flows from investing activities:
Additions to property and equipment	(12,320)	(8,895)
Purchase of marketable security investments	(3,590)	(43,962)
Proceeds from marketable security investments	20,276	11,077
Investment in software	(690)	0
Cost of acquisitions, net of cash acquired	(199,130)	0
Decrease in other	564	743
Net cash used by investing activities	(194,890)	(41,037)
Cash flows from financing activities:
Increase in net borrowings on revolving line of credit	85,000	0
Purchase of treasury shares	(17,786)	0
Proceeds from exercise of stock options	6,528	19,298
Contributions from employee stock purchase plan	2,349	1,798
Net cash provided by financing activities	76,091	21,096
Net (decrease) increase in cash and cash equivalents	(94,842)	24,690
Cash and cash equivalents at beginning of period	134,279	185,926
Cash and cash equivalents at end of period	$ 39,437	$ 210,616