Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income (loss)		$ (3,595)	$ 4,787
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization		17,106	14,929
Deferred taxes		10,638	(899)
Provisions and releases for bad debt and sales-related allowances		(1,219)	2,822
Provision for inventory obsolescence		1,650	752
Stock-based compensation		6,770	10,280
Non-cash accretion of interest expense on convertible notes and imputed financing obligation		3,802	3,672
Other non-cash charges and credits		172	2,486
Changes in operating assets and liabilities, net of effect of acquired businesses		(29,031)	(23,931)
Net cash provided by operating activities		6,293	14,898
Cash flows from investing activities:
Purchases of short-term investments			(35,149)
Proceeds from sales and maturities of short-term investments		7,318	38,235
Purchases of restricted investments	[1]		(1,038)
Purchases, net of proceeds from sales, of property and equipment		(4,214)	(3,789)
Businesses purchased, net of cash acquired		(252)	(5,700)
Net cash provided by (used for) investing activities	[1]	2,852	(7,441)
Cash flows from financing activities:
Proceeds from issuance of common stock		5,010	5,855
Purchases of treasury stock and net share settlements		(17,601)	(22,455)
Repayment of imputed financing obligation related to build-to-suit lease		(254)	(411)
Contingent consideration payments related to businesses acquired		(698)	(1,265)
Net cash used for financing activities		(13,543)	(18,276)
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash equivalents		332	969
Decreases in cash, cash equivalents, and restricted cash equivalents		(4,066)	(9,850)
Cash, cash equivalents, and restricted cash equivalents at beginning of period	[1]	202,876	165,455
Cash, cash equivalents, and restricted cash equivalents at end of period	[1]	$ 198,810	$ 155,605

[1] Certain prior period amounts have been revised due to the implementation of ASU 2016-18. See Note 1 for details.