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 income	$ 29,251	$ 10,154	$ 11,768
Adjustments to reconcile net income to net cash from operating activities:
Provision for doubtful accounts	453	648	276
Reserve for product returns	2,055	2,071	1,559
Amortization on patents and tooling	965	786	391
Amortization and depreciation	17,734	6,490	5,808
Amortization of debt issuance costs	97	103	108
Deferred income taxes	2,488	263	(2,670)
Change in fair value of contingent liability	0	(230)	(470)
Undistributed losses from equity investees	120	81	681
Stock-based compensation	7,413	4,001	3,347
Disposal of property and equipment	828	0	0
Changes in operating assets and liabilities (net of business acquisitions):
Accounts receivable	(1,911)	(11,181)	(5,910)
Inventory	(3,335)	(4,068)	378
Other assets	(2,542)	(837)	(2,725)
Accounts payable, accrued expenses and other current liabilities	3,774	10,458	5,966
Deferred revenue	(517)	636	1,081
Other liabilities	314	3,225	8,431
Cash flows from operating activities	57,187	22,600	28,019
Cash flows used in investing activities:
Business acquisitions, net of cash acquired	(154,289)	0	(5,632)
Additions to property and equipment	(10,464)	(9,055)	(10,347)
Investment in cost and equity method investees	(42)	(139)	(247)
Issuances of notes receivable	(8,000)	(3,073)	(406)
Receipt of payment on notes receivable	4,000	2,441	0
Purchases of licenses to patents	0	(1,600)	(1,000)
Cash flows used in investing activities	(168,795)	(11,426)	(17,632)
Cash flows from financing activities:
Proceeds from issuance of common stock from initial public offering, net of underwriting discount and commission	0	0	97,976
Proceeds from credit facility	139,000	0	0
Repayments of credit facility	(74,700)	0	0
Payments of debt issuance costs	(438)	(131)	0
Payments of long-term consideration for business acquisitions	0	(417)	(417)
Dividends paid to common stockholders	0	0	(1,013)
Dividends paid to employees for unvested shares	0	0	(57)
Dividends paid to redeemable convertible preferred stockholders	0	0	(18,930)
Payments of offering costs	0	0	(2,632)
Repurchases of common stock	(9)	(11)	(1)
Proceeds from early exercise of stock-based awards	0	0	129
Issuances of common stock from equity based plans	3,450	1,661	344
Cash flows from financing activities	67,303	1,102	75,399
Net (decrease) / increase in cash and cash equivalents	(44,305)	12,276	85,786
Cash and cash equivalents at beginning of the period	140,634	128,358	42,572
Cash and cash equivalents at end of the period	96,329	140,634	128,358
Supplemental disclosures:
Cash paid for interest	2,010	181	175
Cash paid for income taxes, net of refunds	1,805	6,021	8,508
Noncash investing and financing activities:
Conversion of redeemable convertible preferred stock to common stock	0	0	202,456
Assumed options from business acquisition	1,375	0	0
Cash not yet paid for business acquisitions	0	0	417
Contingent liability from business acquisition	0	0	230
Cash not yet paid for capital expenditures	322	1,235	625
Reclassification of deferred offering costs to additional paid-in capital	$ 0	$ 0	$ 5,024