Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 11,000	$ 25,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	48,029	40,734
Deferred taxes	(9,149)	(22,127)
Provisions for bad debt and sales-related allowances	10,868	7,558
Provision for inventory obsolescence	3,642	4,492
Stock-based compensation, net of cash settlements	22,541	26,743
Non-cash accretion of interest expense on convertible notes and imputed financing obligation	11,211	9,991
Other non-cash charges and credits	3,254	5,920
Changes in operating assets and liabilities, net of effect of acquired businesses	(58,955)	(42,487)
Net cash provided by operating activities	42,441	55,824
Cash flows from investing activities:
Purchases of short-term investments	(87,623)	(195,904)
Proceeds from sales and maturities of short-term investments	164,979	223,206
Purchases of restricted investments and cash equivalents	(21,459)	(3,745)
Purchases, net of proceeds from sales, of property and equipment	(8,745)	(17,611)
Businesses purchased, net of cash acquired	(16,739)	(19,614)
Net cash provided by (used for) investing activities	30,413	(13,668)
Cash flows from financing activities:
Proceeds from issuance of common stock	11,730	10,359
Purchases of treasury stock and net share settlements	(56,937)	(65,354)
Repayment of debt assumed through business acquisitions and debt issuance costs	(10,786)	(8,539)
Contingent consideration payments related to businesses acquired	(9,512)	(1,868)
Net cash used for financing activities	(65,505)	(65,402)
Effect of foreign exchange rate changes on cash and cash equivalents	4,168	2,158
Increase (decrease) in cash and cash equivalents	11,517	(21,088)
Cash and cash equivalents at beginning of period	164,313	164,091
Cash and cash equivalents at end of period	$ 175,830	$ 143,003