Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income	$ 23,211	$ 21,799
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	27,902	22,682
Deferred taxes	(7,933)	(10,257)
Tax benefit from employee stock plans	1,820	10,176
Excess tax benefit from stock-based compensation	(298)	(11,314)
Provision for bad debts and sales-related allowances	3,724	2,520
Provision for inventory obsolescence	3,627	3,799
Stock-based compensation, net of cash settlements	27,777	25,151
Contingent consideration payments related to businesses acquired		(1,428)
Non-cash accretion of interest expense on convertible notes and imputed financing obligation	9,692	1,387
Other non-cash charges and credits	1,220	(2,638)
Changes in operating assets and liabilities, net of effect of acquired companies	(49,753)	(15,138)
Net cash provided by operating activities	40,989	46,739
Cash flows from investing activities:
Purchases of short-term investments	(243,065)	(70,587)
Proceeds from sales and maturities of short-term investments	247,821	90,349
Purchases, net of proceeds from sales, of property and equipment	(13,146)	(12,938)
Businesses purchased, net of cash acquired	(65,480)	(20,745)
Net cash used for investing activities	(73,870)	(13,921)
Cash flows from financing activities:
Proceeds from issuance of convertible notes, net of debt issuance cost payments	(58)	337,207
Purchase of convertible note hedges		(63,928)
Proceeds from issuance of warrants		34,535
Proceeds from issuance of common stock	11,352	16,196
Purchases of treasury stock and net share settlements	(50,892)	(88,816)
Repayment of debt assumed through business acquisitions	(22,531)	(525)
Contingent consideration payments related to businesses acquired	(3,034)	(9,359)
Excess tax benefit from stock-based compensation	298	11,314
Net cash provided by (used for) financing activities	(64,865)	236,624
Effect of foreign exchange rate changes on cash and cash equivalents	(1,435)	(1,152)
Increase (decrease) in cash and cash equivalents	(99,181)	268,290
Cash and cash equivalents at beginning of period	298,133	177,084
Cash and cash equivalents at end of period	$ 198,952	$ 445,374