Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 109,857	$ 64,869	$ 58,940
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	50,301	19,574	14,605
Share-based compensation expense	29,747	20,182	14,819
Provision for losses - accounts receivable	4,484	1,756	1,897
Deferred income tax benefit	(28,939)	(7,956)	(3,804)
Changes in operating assets and liabilities, exclusive of effects of acquired companies:
Accounts receivable	(30,227)	(28,172)	(8,912)
Income tax receivable	18,185	24,255	29,117
Prepaid expenses and other current assets	2,229	(3,054)	(3,696)
Accounts payable	387	652	1,586
Accrued liabilities	10,717	490	6,326
Deferred revenue	25,118	41,731	31,961
Net cash provided by operating activities	191,859	134,327	142,839
Cash flows from investing activities:
Cost of acquisitions, net of cash acquired	(9,394)	(339,961)	(3,242)
Purchase of cost method investment	0	(15,000)	0
Purchase of marketable security investments	(20,316)	(31,907)	0
Proceeds from marketable security investments	16,837	900	808
Additions to property and equipment	(37,726)	(12,501)	(9,343)
(Increase) decrease in other	(121)	10	222
Net cash used by investing activities	(50,720)	(398,459)	(11,555)
Cash flows from financing activities:
(Decrease) increase in net borrowings on revolving line of credit	(56,000)	66,000	0
Purchase of treasury shares	(111,838)	(645)	(22,817)
Contributions from employee stock purchase plan	6,236	4,671	4,144
Proceeds from exercise of stock options	23,527	23,160	14,680
Debt issuance costs	0	(2,134)	0
Net cash (used) provided by financing activities	(138,075)	91,052	(3,993)
Net increase (decrease) in cash and cash equivalents	3,064	(173,080)	127,291
Cash and cash equivalents at beginning of period	33,087	206,167	78,876
Cash and cash equivalents at end of period	$ 36,151	$ 33,087	$ 206,167