CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net (loss) income	$ (13,555)	$ 48,219	$ 2,480
Adjustments to reconcile net (loss) income to net cash provided by (used in) operating activities:
Depreciation and amortization	22,337	25,479	20,088
(Recovery) provision for doubtful accounts	(340)	886	(23)
Stock-based compensation expense	8,311	7,916	9,514
Non-cash provision for restructuring	3,191	1,137	0
Non-cash interest expense	8,951	9,620	2,890
Unrealized foreign currency transaction losses (gains)	7,336	(2,599)	(7,013)
Benefit from deferred taxes	(873)	(1,842)	(6,693)
Changes in operating assets and liabilities:
Accounts receivable	3,800	14,321	2,442
Inventories	12,280	(2,628)	3,056
Prepaid expenses and other current assets	(7,567)	(1,839)	10,000
Accounts payable	3,606	(18,959)	11,232
Accrued expenses, compensation and benefits and other liabilities	(8,189)	(6,280)	(11,842)
Income taxes payable	800	(9)	(1,041)
Deferred revenues	(31,152)	(122,617)	(69,116)
Net cash provided by (used in) operating activities	8,936	(49,195)	(34,026)
Cash flows from investing activities:
Purchases of property and equipment	(7,877)	(11,003)	(15,330)
Increase in other long-term assets	(36)	(30)	(43)
Payments for business acquisitions, net of cash acquired	0	0	(65,967)
Decrease (increase) in restricted cash	1,790	(4,544)	(456)
Net cash used in investing activities	(6,123)	(15,577)	(81,796)
Cash flows from financing activities:
Proceeds from long-term debt	16,694	100,000	120,401
Repayment of debt	(6,735)	(3,750)	0
Payments for repurchase of common stock	0	0	(7,999)
Cash paid for capped call transaction	0	0	(10,125)
Proceeds from issuance of common stock under employee stock plans	445	6,184	5,035
Common stock repurchases for tax withholdings for net settlement of equity awards	(1,329)	(941)	(1,559)
Proceeds from revolving credit facilities	0	25,000	70,500
Payments on revolving credit facilities	0	(30,000)	(65,500)
Payments for credit facility issuance costs	(700)	(5,041)	(1,195)
Net cash provided by financing activities	8,375	91,452	109,558
Effect of exchange rate changes on cash and cash equivalents	1,087	366	(890)
Net increase (decrease) in cash and cash equivalents	12,275	27,046	(7,154)
Cash and cash equivalents at beginning of period	44,948	17,902	25,056
Cash and cash equivalents at end of period	57,223	44,948	17,902
Supplemental information: [Abstract]
Cash (refunded) paid for income taxes, net	(100)	1,587	2,251
Cash paid for interest	10,966	9,302	3,456
Non-cash transaction - property and equipment included in accounts payable or accruals	30	119	500
Non-cash transaction - unpaid issuance costs for long-term debt	$ 0	$ 0	$ 130