Align Technology (ALGN) 10-Q 3 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 27, 2018
Document Information [Line Items]
Trading Symbol	ALGN
Entity Registrant Name	ALIGN TECHNOLOGY INC
Entity Central Index Key	1,097,149
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		80,149,641

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Net revenues	$ 436,924	$ 310,341
Cost of net revenues	109,516	74,716
Gross profit	327,408	235,625
Operating expenses:
Selling, general and administrative	199,625	151,148
Research and development	29,591	22,804
Total operating expenses	229,216	173,952
Income from operations	98,192	61,673
Interest income	2,176	1,195
Other income (expense), net	177	450
Net income before provision for (benefit from) income taxes and equity in losses of investee	100,545	63,318
Provision for (benefit from) income taxes	2,902	(7,223)
Equity in losses of investee, net of tax	1,777	1,121
Net income	$ 95,866	$ 69,420
Net income per share:
Basic (in usd per share)	$ 1.20	$ 0.87
Diluted (in usd per share)	$ 1.17	$ 0.85
Shares used in computing net income per share:
Basic (in shares)	80,036	79,904
Diluted (in shares)	81,628	81,534

CONDENSED CONSOLIDATED STATEME3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 95,866	$ 69,420
Net change in foreign currency translation adjustment	1,042	(459)
Change in unrealized gains (losses) on investments, net of tax	(129)	15
Other comprehensive income (loss)	913	(444)
Comprehensive income	$ 96,779	$ 68,976

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 498,003	$ 449,511
Marketable securities, short-term	164,740	272,031
Accounts receivable, net of allowance for doubtful accounts of $2,735 and $5,814, respectively	361,459	324,189
Inventories	35,866	31,688
Prepaid expenses and other current assets	108,708	80,948
Total current assets	1,168,776	1,158,367
Marketable securities, long-term	10,212	39,948
Property, plant and equipment, net	400,528	348,793
Equity method investments	52,829	54,606
Goodwill and intangible assets, net	87,629	89,068
Deferred tax assets	45,524	49,334
Other assets	17,233	43,893
Total assets	1,782,731	1,784,009
Current liabilities:
Accounts payable	41,881	36,776
Accrued liabilities	180,093	195,562
Deferred revenues	296,011	267,713
Total current liabilities	517,985	500,051
Income tax payable	119,349	114,091
Other long-term liabilities	17,937	15,579
Total liabilities	655,271	629,721
Commitments and contingencies (Notes 8 and 9)
Stockholders' equity:
Preferred stock, $0.0001 par value (5,000 shares authorized; none issued)	0	0
Common stock, $0.0001 par value (200,000 shares authorized; 80,144 and 80,040 issued and outstanding, respectively)	8	8
Additional paid-in capital	858,632	886,435
Accumulated other comprehensive income (loss), net	1,484	571
Retained earnings	267,336	267,274
Total stockholders’ equity	1,127,460	1,154,288
Total liabilities and stockholders’ equity	$ 1,782,731	$ 1,784,009

CONDENSED CONSOLIDATED BALANCE5

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts receivable, allowance for doubtful accounts and returns	$ 2,735	$ 5,814
Preferred stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000	5,000
Preferred stock, shares issued	0	0
Common stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000	200,000
Common stock, shares issued	80,144	80,040
Common stock, shares outstanding	80,144	80,040

CONDENSED CONSOLIDATED STATEME6

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	$ 95,866	$ 69,420
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred taxes	4,069	7,789
Depreciation and amortization	11,434	7,867
Stock-based compensation	15,830	14,812
Equity in losses of investee	1,777	1,121
Other non-cash operating activities	474	2,079
Changes in assets and liabilities, net of effects of acquisitions:
Accounts receivable	(36,026)	(24,525)
Inventories	(4,002)	(7,923)
Prepaid expenses and other assets	(15,873)	(527)
Accounts payable	5,599	5,522
Accrued and other long-term liabilities	(35,466)	(40,891)
Long-term income tax payable	5,259	1,189
Deferred revenues	28,391	11,688
Net cash provided by operating activities	77,332	47,621
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions, net of cash acquired	0	(8,953)
Purchase of property, plant and equipment	(57,578)	(59,569)
Purchase of marketable securities	0	(169,777)
Proceeds from maturities of marketable securities	126,825	87,003
Proceeds from sales of marketable securities	9,560	11,684
Loan advances to equity investee	0	(8,000)
Loan repayment from equity investee	30,000	0
Other investing activities	462	(850)
Net cash provided by (used in) investing activities	109,269	(148,462)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	8,020	7,288
Common stock repurchases	(100,000)	(3,793)
Employees’ taxes paid upon the vesting of restricted stock units	(47,842)	(36,496)
Net cash used in financing activities	(139,822)	(33,001)
Effect of foreign exchange rate changes on cash and cash equivalents, and restricted cash	1,715	2,430
Net increase (decrease) in cash, cash equivalents, and restricted cash	48,494	(131,412)
Cash, cash equivalents, and restricted cash at beginning of the period	450,125	393,019
Cash, cash equivalents, and restricted cash at end of the period	498,619	261,607
SUPPLEMENTAL CASH FLOW INFORMATION:
Accounts payable or accrued liabilities related to property, plant and equipment	$ 18,739	$ 7,662

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements have been prepared by Align Technology, Inc. (“we”, “our”, or “Align”) in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) and contain all adjustments, including normal recurring adjustments, necessary to state fairly our results of operations for the three months ended March 31, 2018 and 2017 , our comprehensive income for the three months ended March 31, 2018 and 2017 , our financial position as of March 31, 2018 and our cash flows for the three months ended March 31, 2018 and 2017 . The Condensed Consolidated Balance Sheet as of December 31, 2017 was derived from the December 31, 2017 audited financial statements and have been recast to reflect the adoption of accounting standards as described below. It does not include all disclosures required by accounting principles generally accepted in the United States of America (“U.S.”). During the first quarter of fiscal year 2018, we adopted the Accounting Standards Codification (“ASC”) 606, “ Revenues from Contracts with Customers, ” using the full retrospective method and Accounting Standards Update (“ASU”) 2016-18, “Statement of Cash Flows - Restricted Cash,” on a retrospective basis. Condensed Consolidated Balance Sheet as of December 31, 2017 and Condensed Consolidated Statement of Cash Flow for the three months ended March 31, 2017 have been recast to comply with the adoption of these standards. The results of operations for the three months ended March 31, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 or any other future period, and we make no representations related thereto. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” “Quantitative and Qualitative Disclosures About Market Risk” and the Consolidated Financial Statements and notes thereto included in Items 7, 7A and 8, respectively, in our Annual Report on Form 10-K for the year ended December 31, 2017 . Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles (“GAAP”) in the U.S. requires our management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates. On an ongoing basis, we evaluate our estimates, including those related to the fair values of financial instruments, long-lived assets and goodwill, equity method investments, useful lives of intangible assets and property and equipment, revenue recognition, stock-based compensation, income taxes and contingent liabilities, among others. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Significant Accounting Policies Our significant accounting policies are described in Note 1 “Summary of Significant Accounting Policies” of the Notes to Consolidated Financial Statements included in our Annual Report on Form 10-K. Significant changes to the Revenue Recognition policy as a result of ASC 606 adoption are discussed below: Revenue Recognition Our revenues are derived primarily from the sale of aligners, scanners, and services from our Clear Aligner and Scanner segments. We enter into sales contracts that may consist of multiple distinct performance obligations where certain performance obligations of the sales contract are not delivered in one reporting period. We measure and allocate revenue according to Accounting Standards Codification (“ASC”) 606-10, “ Revenues from Contracts with Customers ”. We identify a performance obligation as distinct if both the following criteria are true: the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer and the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract. Determining the standalone selling price (“SSP”) and allocation of consideration from a contract to the individual performance obligations, and the appropriate timing of revenue recognition, is the result of significant qualitative and quantitative judgments. Management considers a variety of factors such as historical sales, usage rates, costs, and expected margin, which may vary over time depending upon the unique facts and circumstances related to each performance obligation in making these estimates. While changes in the allocation of the SSP between performance obligations will not affect the amount of total revenue recognized for a particular contract, any material changes could impact the timing of revenue recognition, which would have a material effect on our financial position and result of operations. This is because the contract consideration is allocated to each performance obligation, delivered or undelivered, at the inception of the contract based on the SSP of each distinct performance obligation. Clear Aligner We enter into contracts (“treatment plan(s)”) that involve multiple future performance obligations. Invisalign Full, Invisalign Teen, and Invisalign Assist products include optional additional aligners at no charge for a period of up to five years after initial shipment and Invisalign Go includes optional additional aligners at no charge for a period of up to two years after initial shipment. Invisalign Teen also includes up to six optional replacement aligners in the price of the product and may be ordered by the dental professional any time throughout treatment. Invisalign Lite includes one optional case refinement in the price of the product. Case refinement is a finishing tool used to adjust a patient’s teeth to the desired final position and may be elected by the dental professional at any time during treatment; however, it is generally ordered in the last stages of orthodontic treatment. We determined that our treatment plans comprise the following performance obligations that also represent distinct deliverables: initial aligners, additional aligners, case refinement, and replacement aligners. The Company elected to take the practical expedient to consider shipping and handling costs as activities to fulfill the performance obligation. We allocate revenue for each treatment plan based on each unit’s SSP and recognize the revenue over the manufacturing period, typically 1-3 days, as the aligners do not have an alternative use and we have enforceable rights to payment. As we collect most consideration upfront, we considered whether a significant financing component exists. However, as the delivery of the performance obligations are at the customer’s discretion, we concluded that no significant financing component exists. Scanners We sell intraoral scanners and CAD/CAM services through both our direct sales force and distribution partners. The intraoral scanner sales price includes one year of warranty and unlimited scanning services. The customer may, for additional fees, also select extended warranty and unlimited scanning services for periods beyond the initial year. When intraoral scanners are sold with an unlimited scanning service agreement and/or extended warranty, we allocate revenue based on each element’s SSP. We estimate the SSP of each element, taking into consideration historical prices as well as our discounting strategies. Revenue is then recognized over time as the monthly services are rendered and upon shipment for the scanner, as that is when we deem the customer to have obtained control. Warranties For both Clear Aligner and iTero scanner segments, the Company offers an assurance warranty, which provides the customer assurance that the product will function as the parties intended because it complies with agreed-upon specifications, and thus is not treated as a separate performance obligation and will continue to be accrued in accordance with the FASB guidance on guarantees. Volume Discounts In certain situations, we offer promotions in which the discount will increase depending upon the volume purchased over time. We concluded that in these situations, the promotions can represent either variable consideration or options, depending upon the specifics of the promotion. In the event the promotion contains an option, the option is considered a material right and therefore, included in the accounting for the initial arrangement. We estimate the average anticipated discount over the lifetime of the promotion or contract, and apply that discount to each unit as it is sold. On a quarterly basis, we review our estimates and if needed, updates are made and changes are applied prospectively. Costs to Obtain a Contract We offer a variety of commission plans to our salesforce; each plan has multiple components. To match the costs to obtain a contract to the associated revenue, we evaluate the individual components and capitalize the eligible components, recognizing the costs over the treatment period. Unfulfilled Performance Obligations for Clear Aligners and Scanners The Company’s unfilled performance obligations as of March 31, 2018 and the estimated revenue expected to be recognized in the future related to these performance obligations are $309 million . This includes performance obligations from the Clear Aligner segment, primarily the shipment of additional aligners, which are fulfilled over 1-5 years, and performance obligations from the iTero scanner segment, primarily contracted deliveries of additional scanners and support, which are fulfilled over 1-5 years. The estimate includes both product and service unfulfilled performance obligations and the time range reflect our best estimate of when the Company will transfer control to the customer and may change based on customer usage patterns, timing of shipments, readiness of customers’ facilities for installation, and manufacturing availability. Contract Balances The timing of revenue recognition results in deferred revenues on the Condensed Consolidated Balance Sheet. We usually collect the entire treatment fee prior to all performance obligations being performed and payment terms vary from net 30 to net 90. Contract liabilities are recorded as deferred revenue balances, which are generated based upon timing of invoices and recognition patterns, not payments. If the revenue recognition exceeds the billing, the exceeded amount is considered unbilled receivable and a contract asset. Conversely, if the billing occurs prior to the revenue recognition, the amount is considered deferred revenue and a contract liability. Recent Accounting Pronouncements (i) New Accounting Updates Recently Adopted In May 2014, the Financial Accounting Standards Board (“FASB”) released ASU 2014-9, “ Revenue from Contracts with Customers, ” (Topic 606) to supersede nearly all existing revenue recognition guidance under GAAP. The core principle of the standard is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for the goods or services. We adopted the guidance in the first quarter of fiscal year 2018 by applying the full retrospective method. We have completed the financial statement impact of adoption including, but not limited to, volume-based discount programs, sales commissions and the identification of performance obligations. The impact of adoption was primarily related to the Clear Aligner segment. Our disaggregation of revenue can be found in Note 14 “Segments and Geographical Information.” The Company elected to take the practical expedient to exclude from the transaction price all taxes assessed by a governmental authority. In preparation for adoption of the standard, we have reviewed and, where necessary, implemented additional key system functionalities and internal controls to enable the preparation of financial information. Prior periods have been retrospectively adjusted, and we recognized cumulative effect of adopting the guidance as an adjustment to our opening balance of retained earnings as of January 1, 2016. The adoption of ASU 2014-09 did not have a material impact on our Condensed Consolidated Statements of Operations, Condensed Consolidated Statements of Comprehensive Income or Condensed Consolidated Statements of Cash Flows for the historical periods presented in the Item 1 Financial Statements section. Consolidated balance sheet line items, which reflect the adoption of the ASU 2014-09 are as follows (in thousands): December 31, 2017 As Previously Reported Adjustment As Adjusted Asset Accounts: Accounts receivable, net $ 322,825 $ 1,364 $ 324,189 Deferred tax assets 50,059 (725 ) 49,334 Other assets 38,379 5,514 43,893 Liability and Stockholders’ Equity Accounts: Accrued liabilities $ 194,198 $ 1,364 $ 195,562 Deferred revenues 266,842 871 267,713 Retained earnings 263,356 3,918 267,274 In August 2016, the FASB issued ASU 2016-15, “Classification of Certain Cash Receipts and Cash Payments,” which clarifies the presentation and classification of certain cash receipts and cash payments in the statements of cash flows. The amendments are effective for fiscal years and interim periods within those years beginning after December 15, 2017. We adopted the standard in the first quarter of fiscal year 2018 on a retrospective basis which did not have an impact on our consolidated statements of cash flows. In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows - Restricted Cash,” which provides guidance to address the classification and presentation of changes in restricted cash in the statements of cash flows . The amendments are effective for fiscal years and interim periods within those years beginning after December 15, 2017 on a retrospective basis. We adopted the guidance in the first quarter of fiscal year 2018 on a retrospective basis and presented the changes in the total of cash, cash equivalents, and restricted cash in the consolidated statements of cash flows. Consolidated statement of cash flows line items, which reflect the adoption of the ASU 2016-18, are as follows (in thousands): March 31, 2017 As Previously Reported Adjustment As Adjusted Cash Flows from Investing Activities Other investing activities $ 2,314 $ (3,164 ) $ (850 ) Net cash provided by (used in) investing activities (145,298 ) (3,164 ) (148,462 ) Net increase (decrease) in cash, cash equivalent, and restricted cash (128,248 ) (3,164 ) (131,412 ) Cash, cash equivalents, and restricted cash at beginning of the period 389,275 3,744 393,019 Cash, cash equivalents, and restricted cash at end of the period $ 261,027 $ 580 $ 261,607 In May 2017, the FASB issued ASU 2017-09, “ Compensation — Stock Compensation (Topic 718): Scope of Modification Accounting,” to clarify when to account for a change to the terms or conditions of a share-based payment award as a modification. The amendments are effective for fiscal years and interim periods within those years beginning after December 15, 2017 on a prospective basis. We adopted the standard in the first quarter of fiscal year 2018 on a prospective basis which did not have an impact on our consolidated financial statements and related disclosures. (ii) Recent Accounting Updates Not Yet Effective In February 2016, the FASB issued ASU 2016-02, “ Leases ” (Topic 842) to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The updated guidance is effective for annual periods beginning after December 15, 2018, including interim periods within those fiscal years. We plan to adopt the standard in the first quarter of fiscal year 2019 by electing practical expedients available in the standard. While we are currently evaluating the impact of the adoption of this guidance on our consolidated financial statements, we expect the adoption will have a material increase in assets and liabilities on our consolidated balance sheet. In June 2016, the FASB issued ASU 2016-13, “ Financial Instruments - Credit Losses ” (Topic 326) . The FASB issued this update to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. The amendments in this update replace the existing guidance of incurred loss impairment methodology with an approach that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The updated guidance is effective for annual periods beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption of the update is permitted in fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. We are currently evaluating the impact of this guidance on our consolidated financial statements and related disclosures. In January 2017, the FASB issued ASU 2017-04, “Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment,” to simplify the subsequent measurement of goodwill by eliminating step two from the goodwill impairment test. Under the amendments, an entity will recognize an impairment charge for the amount by which the carrying value exceeds the fair value. The amendments are effective for fiscal years and interim periods within those years beginning after December 15, 2019 on a prospective basis and early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements and related disclosures. In February 2018, the FASB issued ASU 2018-02, “Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income,” which gives entities the option to reclassify to retained earnings the tax effects resulting from the U.S. Tax Cuts and Jobs Act (the “TCJA”) related to items in accumulated other comprehensive income. The amendments are effective for fiscal years and interim periods within those years beginning after December 15, 2018 on a retrospective basis and early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements and related disclosures.

Marketable Securities and Fair

Marketable Securities and Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Marketable Securities and Fair Value Measurements	Marketable Securities and Fair Value Measurements As of March 31, 2018 and December 31, 2017, the estimated fair value of our short-term and long-term marketable securities, classified as available for sale, are as follows (in thousands): Short-term March 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Commercial paper $ 20,447 $ — $ (1 ) $ 20,446 Corporate bonds 106,583 1 (333 ) 106,251 U.S. government agency bonds 8,999 — (52 ) 8,947 U.S. government treasury bonds 28,146 — (51 ) 28,095 Certificates of deposit 1,001 — — 1,001 Total marketable securities, short-term $ 165,176 $ 1 $ (437 ) $ 164,740 Long-term March 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. government agency bonds $ 7,032 $ — $ (66 ) $ 6,966 Corporate bonds 3,265 1 (20 ) 3,246 Total marketable securities, long-term $ 10,297 $ 1 $ (86 ) $ 10,212 Short-term December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Commercial paper $ 58,503 $ — $ (1 ) $ 58,502 Corporate bonds 145,728 3 (174 ) 145,557 U.S. government agency bonds 3,013 — (7 ) 3,006 U.S. government treasury bonds 60,650 — (70 ) 60,580 Certificates of deposit 4,386 — — 4,386 Total marketable securities, short-term $ 272,280 $ 3 $ (252 ) $ 272,031 Long-term December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. government agency bonds $ 15,023 $ — $ (68 ) $ 14,955 Corporate bonds 25,067 2 (76 ) 24,993 Total marketable securities, long-term $ 40,090 $ 2 $ (144 ) $ 39,948 Cash equivalents are not included in the table above as the gross unrealized gains and losses are not material. We have no short-term or long-term investments that have been in a continuous material unrealized loss position for greater than twelve months as of March 31, 2018 and December 31, 2017. Amounts reclassified to earnings from accumulated other comprehensive income (loss), net related to unrealized gains or losses were not material for the three months ended March 31, 2018 and 2017. For the three months ended March 31, 2018 and 2017, realized gains or losses were not material. Our fixed-income securities investment portfolio consists of investments that have a maximum effective maturity of 40 months on any individual security. The securities that we invest in are generally deemed to be low risk based on their credit ratings from the major rating agencies. The longer the duration of these securities, the more susceptible they are to changes in market interest rates and bond yields. As interest rates increase, those securities purchased at a lower yield show a mark-to-market unrealized loss. The unrealized losses are due primarily to changes in credit spreads and interest rates. We expect to realize the full value of all these investments upon maturity or sale. The weighted average remaining duration of these securities was approximately five months and six months as of March 31, 2018 and December 31, 2017 , respectively. As the carrying value approximates the fair value for our short-term and long-term marketable securities shown in the tables above, the following table summarizes the fair value of our short-term and long-term marketable securities classified by maturity as of March 31, 2018 and December 31, 2017 (in thousands): March 31, 2018 December 31, 2017 One year or less $ 164,740 $ 272,031 Due in greater than one year 10,212 39,948 Total available for sale short-term and long-term marketable securities $ 174,952 $ 311,979 Fair Value Measurements We measure the fair value of financial assets as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. We use the GAAP fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. This hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The three levels of inputs that may be used to measure fair value: Level 1 — Quoted (unadjusted) prices in active markets for identical assets or liabilities. Our Level 1 assets consist of money market funds and U.S. government treasury bonds. We did not hold any Level 1 liabilities as of March 31, 2018 and December 31, 2017. Level 2 — Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the asset or liability. Our Level 2 assets consist of commercial paper, corporate bonds, U.S. government agency bonds, certificates of deposit and our Israeli funds that are mainly invested in insurance policies. We obtain fair values for our Level 2 investments. Our custody bank and asset managers independently use professional pricing services to gather pricing data which may include quoted market prices for identical or comparable financial instruments, or inputs other than quoted prices that are observable either directly or indirectly, and we are ultimately responsible for these underlying estimates. We did not hold any Level 2 liabilities as of March 31, 2018 and December 31, 2017. Level 3 — Unobservable inputs to the valuation methodology that are supported by little or no market activity and that are significant to the measurement of the fair value of the assets or liabilities. Level 3 assets and liabilities include those whose fair value measurements are determined using pricing models, discounted cash flow methodologies or similar valuation techniques, as well as significant management judgment or estimation. Certain investments in private companies contain embedded derivatives, which do not require bifurcation as we elected to measure these investments at fair value. Our Level 3 assets consist of convertible short-term notes receivable. The following table summarizes the reconciliation of assets measured and recorded at fair value on a recurring basis using significant unobservable inputs Level 3 (in thousands): Notes Receivable Balance as of December 31, 2017 $ 4,476 Accrued interest receivable 25 Change in fair value recognized in earnings 358 Balance as of March 31, 2018 $ 4,859 Subsequent to March 31, 2018, in April 2018, the convertible notes receivable issued to a privately held company was converted into equity shares as a result of qualified financing secured by the company. We did not hold any Level 3 liabilities as of March 31, 2018 and December 31, 2017. The following tables summarize our financial assets measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017 (in thousands): Description Balance as of March 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Other Cash equivalents: Money market funds $ 255,373 $ 255,373 $ — $ — Short-term investments: Commercial paper 20,446 — 20,446 — Corporate bonds 106,251 — 106,251 — U.S. government agency bonds 8,947 — 8,947 — U.S. government treasury bonds 28,095 28,095 — — Certificates of deposit 1,001 — 1,001 — Long-term investments: U.S. government agency bonds 6,966 — 6,966 — Corporate bonds 3,246 — 3,246 — Prepaid expenses and other current assets: Israeli funds 3,114 — 3,114 — Short-term notes receivable 4,859 — — 4,859 $ 438,298 $ 283,468 $ 149,971 $ 4,859 Description Balance as of December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Other Cash equivalents: Money market funds $ 253,155 $ 253,155 $ — $ — Commercial paper 7,246 — 7,246 — Corporate bonds 2,016 — 2,016 — Short-term investments: Commercial paper 58,502 — 58,502 — Corporate bonds 145,557 — 145,557 — U.S. government agency bonds 3,006 — 3,006 — U.S. government treasury bonds 60,580 60,580 — — Certificates of deposit 4,386 — 4,386 — Long-term investments: U.S. government agency bonds 14,955 — 14,955 — Corporate bonds 24,993 — 24,993 — Prepaid expenses and other current assets: Israeli funds 3,075 — 3,075 — Short-term notes receivable 4,476 — — 4,476 $ 581,947 $ 313,735 $ 263,736 $ 4,476 Derivative Financial Instruments In March 2018, we began entering into foreign currency forward contracts to minimize the short-term impact of foreign currency exchange rate fluctuations on certain trade and intercompany receivables and payables. These forward contracts are classified within level 2 of the fair value hierarchy. There was no net gain or loss from the settlement of foreign currency forward contracts during the three months ended March 31, 2018. As of March 31, 2018 , the fair value of foreign exchange forward contracts outstanding was not material. The following table presents the gross notional value of all our foreign exchange forward contracts outstanding as of March 31, 2018 (in thousands): March 31, 2018 Local Currency Amount Notional Contract Amount (USD) Euro €40,000 $ 49,244 British Pound £9,000 12,615 $ 61,859

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Balance Sheet Components	Balance Sheet Components Inventories Inventories consist of the following (in thousands): March 31, December 31, Raw materials $ 13,386 $ 12,721 Work in process 11,442 12,157 Finished goods 11,038 6,810 Total inventories $ 35,866 $ 31,688 Other Assets Other assets consist of the following (in thousands): March 31, December 31, Capitalized commissions $ 7,681 $ 5,515 Other long-term assets 5,831 4,821 Security deposits 3,721 3,557 Loan receivable — 30,000 Total other assets $ 17,233 $ 43,893 Accrued Liabilities Accrued liabilities consist of the following (in thousands): March 31, December 31, Accrued payroll and benefits $ 69,581 $ 103,004 Accrued expenses 32,458 27,318 Accrued income taxes 17,134 12,405 Accrued fixed assets 15,241 11,362 Accrued warranty 6,657 5,929 Accrued professional fees 6,562 6,316 Accrued sales tax and value added tax 5,340 5,503 Accrued sales rebate 5,121 11,209 Accrued sales return reserve 1 4,887 1,364 Other accrued liabilities 17,112 11,152 Total accrued liabilities $ 180,093 $ 195,562 1 December 31, 2017 balance has been reclassified from accounts receivable, net to reflect the adoption of ASU 2014-09 ( Refer to Note 1 “Summary of Significant Accounting Policies” of the Notes to Condensed Consolidated Financial Statements for more information). Warranty We regularly review the balance for accrued warranty and update based on historical warranty trends. Actual warranty costs incurred have not materially differed from those accrued; however, future actual warranty costs could differ from the estimated amounts. Warranty accrual as of March 31, 2018 and 2017 consists of the following activity (in thousands): Three Months Ended 2018 2017 Balance at beginning of period $ 5,929 $ 3,841 Charged to cost of revenues 2,359 1,822 Actual warranty expenditures (1,631 ) (1,362 ) Balance at end of period $ 6,657 $ 4,301 Deferred Revenues Deferred revenues consist of the following (in thousands): March 31, December 31, Deferred revenues - current $ 296,011 $ 267,713 Deferred revenues - long-term 1 6,171 4,588 1 Included in other long-term liabilities on our Condensed Consolidated Balance Sheets During the three months ended March 31, 2018 and March 31, 2017, the Company recognized revenue of $437 million and $310 million , respectively, of which $86 million and $51 million were included in the deferred revenues balance at December 31, 2017 and December 31, 2016, respectively.

Equity Method Investments

Equity Method Investments	3 Months Ended
	Mar. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	Equity Method Investments On July 25, 2016, we acquired a 17% equity interest, on a fully diluted basis, in SmileDirectClub, LLC (“SDC”) for $46.7 million . The investment is accounted for under an equity method investment and the investee, SDC, is considered a related party. The investment is reported in our Condensed Consolidated Balance Sheet under equity method investments, and we record our proportional share of SDC’s losses within equity in losses of investee, net of tax, in our Condensed Consolidated Statement of Operations. On July 24, 2017, we purchased an additional 2% equity interest in SDC for $12.8 million . As a result of this purchase, we hold a 19% equity interest in SDC on a fully diluted basis. As of March 31, 2018 and December 31, 2017, the balance of our equity method investments was $52.8 million and $54.6 million , respectively. Concurrently with the investment on July 25, 2016, we also entered into a supply agreement with SDC to manufacture clear aligners for SDC’s doctor-led, at-home program for simple teeth straightening. The term of the supply agreement expires on December 31, 2019. We commenced supplying aligners to SDC in October 2016. The sale of aligners to SDC and the income from the supply agreement are reported in our Clear Aligner business segment. We eliminate unrealized profit on outstanding intercompany transactions. As of March 31, 2018 and December 31, 2017, the balance of accounts receivable due from SDC was $8.1 million and $14.3 million , respectively. For the three months ended March 31, 2018 and 2017, net revenues recognized from SDC were $5.3 million and $0.6 million , respectively. On July 25, 2016, we entered into a Loan and Security Agreement (the “Loan Agreement”) with SDC and amended on July 24, 2017 where we agreed to provide SDC a loan of up to $30.0 million in one or more advances. On February 7, 2018, $30.0 million of outstanding loan advances and related accrued interest were repaid in full, and the Loan Agreement was terminate ( Refer to Note 8 “Legal Proceedings” of the Notes to Condensed Consolidated Financial Statements for SDC legal proceedings discussion).

Business Combinations

Business Combinations	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
Business Combinations	Business Combinations During the first quarter of 2017, we completed the acquisitions of certain of our distributors for the total cash consideration of approximately $9.5 million including cash acquired. We recorded $1.9 million of net tangible liabilities, $8.2 million of identifiable intangible assets and $3.2 million of goodwill. The goodwill is primarily related to the benefit we expect to obtain from direct sales as we believe that the transition from our distributor arrangements to a direct sales model will increase our net revenues in the region as we will experience higher average sales prices (“ASP”) compared to our discounted ASP under the distribution agreements. The goodwill is not deductible for tax purposes. Pro forma results of operations for these acquisitions have not been presented as they were not material to our results of operations, either individually or in aggregate, for the three months ended March 31, 2017.

Goodwill and Long-lived Assets

Goodwill and Long-lived Assets	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill The change in the carrying value of goodwill for the three months ended March 31, 2018 , all attributable to our Clear Aligner reporting unit, is as follows (in thousands): Total Balance as of December 31, 2017 $ 64,614 Adjustments 1 7 Balance as of March 31, 2018 $ 64,621 1 The adjustments to goodwill during the period were a result of foreign currency translation. During the fourth quarter of fiscal 2017, we performed the annual goodwill impairment testing and found no impairment as the fair value of our Clear Aligner reporting unit was significantly in excess of the carrying value. Intangible Long-Lived Assets Acquired intangible long-lived assets are being amortized as follows (in thousands): Weighted Average Amortization Period (in years) Gross Carrying Amount as of Accumulated Amortization Accumulated Impairment Loss Net Carrying Trademarks 15 $ 7,100 $ (1,803 ) $ (4,179 ) $ 1,118 Existing technology 13 12,600 (4,845 ) (4,328 ) 3,427 Customer relationships 11 33,500 (15,147 ) (10,751 ) 7,602 Reacquired rights 3 7,500 (1,914 ) — 5,586 Patents 8 6,796 (1,712 ) — 5,084 Other 2 618 (427 ) — 191 Total intangible assets $ 68,114 $ (25,848 ) $ (19,258 ) $ 23,008 Weighted Average Amortization Period (in years) Gross Carrying Amount as of December 31, 2017 Accumulated Amortization Accumulated Impairment Loss Net Carrying Value as of December 31, 2017 Trademarks 15 $ 7,100 $ (1,769 ) $ (4,179 ) $ 1,152 Existing technology 13 12,600 (4,704 ) (4,328 ) 3,568 Customer relationships 11 33,500 (14,681 ) (10,751 ) 8,068 Reacquired rights 3 7,500 (1,356 ) — 6,144 Patents 8 6,798 (1,504 ) — 5,294 Other 2 618 (390 ) — 228 Total intangible assets $ 68,116 $ (24,404 ) $ (19,258 ) $ 24,454 The total estimated annual future amortization expense for these acquired intangible assets as of March 31, 2018 is as follows (in thousands): Fiscal Year Ending December 31, Remainder of 2018 $ 4,843 2019 6,343 2020 3,882 2021 3,389 2022 2,116 Thereafter 2,435 Total $ 23,008 Amortization for the three months ended March 31, 2018 and 2017 was $1.4 million for both periods.

Credit Facilities

Credit Facilities	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Credit Facilities	Credit Facilities On February 27, 2018, we entered into a new credit facility for a $200.0 million revolving line of credit, with a $50.0 million letter of credit sublimit, and a maturity date of February 27, 2021, replacing the existing credit facility which we had $50.0 million revolving line of credit with a $10.0 million letter of credit. The credit facility requires us to comply with specific financial conditions and performance requirements. The loans bear interest, at our option, at either a rate based on the reserve adjusted LIBOR for the applicable interest period or a base rate, in each case plus a margin. The base rate is the highest of the credit facility’s publicly announced prime rate, the federal funds rate plus 0.50% and one month LIBOR plus 1.0% . The margin ranges from 1.25% to 1.75% for LIBOR loans and 0.25% to 0.75% for base rate loans. Interest on the loans is payable quarterly in arrears with respect to base rate loans and at the end of an interest period (and at three month intervals if the interest period exceeds three months) in the case of LIBOR loans. Principal, together with accrued and unpaid interest, is due on the maturity date. As of March 31, 2018, we had no outstanding borrowings under this credit facility and were in compliance with the conditions and performance requirements.

Legal Proceedings (Notes)

Legal Proceedings (Notes)	3 Months Ended
	Mar. 31, 2018
Legal Proceedings [Abstract]
Legal Proceedings	Legal Proceedings Patent Infringement Lawsuit On November 14, 2017, Align filed six patent infringement lawsuits asserting 26 patents against 3Shape A/S, a Danish corporation, and a related U.S. corporate entity, asserting that 3Shape’s Trios intraoral scanning system and Dental System software infringe Align patents. Align filed two Section 337 complaints with the U.S. International Trade Commission (ITC) alleging that 3Shape violates U.S. trade laws by selling for importation and importing its infringing Trios intraoral scanning system and Dental System software. Align’s ITC complaints seek cease and desist orders and exclusion orders prohibiting the importation of 3Shape’s Trios scanning system and Dental System software products into the U.S. Align also filed four separate complaints in the United States District Court for the District of Delaware alleging patent infringement by 3Shape’s Trios intraoral scanning system and Dental System software. All of these district court complaints seek monetary damages and injunctive relief against further infringement. SDC Dispute On April 5, 2018, SDC Financial LLC, SmileDirectClub LLC, and the Members of SDC Financial LLC other than Align (collectively, the "SDC Entities") initiated proceedings that seek, among other forms of relief, to preliminarily and permanently enjoin all activities related to the Invisalign store pilot project, require Align to close the existing Invisalign stores, prohibit Align from opening any additional stores, and allow the SDC Entities to exercise a right to repurchase all of Align's SDC Financial LLC membership interests for a purchase price equal to the current capital account balance. We dispute the allegations that we have breached our obligations to the SDC Entities, including the allegation that the SDC Entities are entitled to exercise a repurchase right and we will oppose and vigorously defend ourselves in the proceedings. This dispute does not impact Align’s existing supply agreement with SDC which remains in place through 2019 and includes a minimum volume commitment. We are currently unable to predict the outcome of this amended complaint and therefore cannot determine the likelihood of loss nor estimate a range of possible loss, if any. In addition, in the course of Align’s operations, Align is involved in a variety of claims, suits, investigations, and proceedings, including actions with respect to intellectual property claims, patent infringement claims, government investigations, labor and employment claims, breach of contract claims, tax, and other matters. Regardless of the outcome, these proceedings can have an adverse impact on us because of defense costs, diversion of management resources, and other factors. Although the results of complex legal proceedings are difficult to predict and Align’s view of these matters may change in the future as litigation and events related thereto unfold; Align currently does not believe that these matters, individually or in the aggregate, will materially affect Align’s financial position, results of operations or cash flows.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Leases As of March 31, 2018 , minimum future lease payments for non-cancelable operating leases are as follows (in thousands): Fiscal Year Ending December 31, Operating Leases Remainder of 2018 $ 13,508 2019 15,061 2020 11,056 2021 9,270 2022 7,107 Thereafter 10,537 Total minimum future lease payments $ 66,539 Sublease income is not material and excluded from the table above. Other Commitments On July 25, 2016, we entered into a Loan and Security Agreement (the “Loan Agreement”) with SmileDirectClub, LLC (“SDC”) and subsequently amended on July 24, 2017 to provide a loan of up to $30.0 million in one or more advances to SDC (the “Loan Facility”). On February 7, 2018, $30.0 million of outstanding advances and related accrued interest were repaid in full, and the Loan Agreement was terminated ( Refer to Note 4 “Equity Method Investments” of the Notes to Condensed Consolidated Financial Statements for more information on our investments in SDC). Off-Balance Sheet Arrangements As of March 31, 2018 , we had no material off-balance sheet arrangements that have, or are reasonably likely to have, a current or future material effect on our consolidated financial condition, results of operations, liquidity, capital expenditures or capital resources other than certain items disclosed in Note 9 “Commitments and Contingencies” of the Notes to Consolidated Financial Statements included in our Annual Report on Form 10-K. Indemnification Provisions In the normal course of business to facilitate transactions in our services and products, we indemnify certain parties: customers, vendors, lessors, and other parties with respect to certain matters, including, but not limited to, services to be provided by us and intellectual property infringement claims made by third parties. In addition, we have entered into indemnification agreements with our directors and our executive officers that will require us, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. Several of these agreements limit the time within which an indemnification claim can be made and the amount of the claim. It is not possible to make a reasonable estimate of the maximum potential amount under these indemnification agreements due to the unique facts and circumstances involved in each particular agreement. Additionally, we have a limited history of prior indemnification claims and the payments we have made under such agreements have not had a material adverse effect on our results of operations, cash flows or financial position. However, to the extent that valid indemnification claims arise in the future, future payments by us could be significant and could have a material adverse effect on our results of operations or cash flows in a particular period. As of March 31, 2018 , we did not have any material indemnification claims that were probable or reasonably possible.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Stockholders' Equity	Stockholders’ Equity Summary of Stock-Based Compensation Expense As of March 31, 2018 , the 2005 Incentive Plan (as amended) has a total reserve of 27,783,379 shares of which 6,302,917 shares are available for issuance. Stock-based compensation is based on the estimated fair value of awards, net of estimated forfeitures, and recognized over the requisite service period. Estimated forfeitures are based on historical experience at the time of grant and may be revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. The stock-based compensation related to all of our stock-based awards and employee stock purchases for the three months ended March 31, 2018 and 2017 is as follows (in thousands): Three Months Ended 2018 2017 Cost of net revenues $ 881 $ 925 Selling, general and administrative 12,578 11,716 Research and development 2,371 2,171 Total stock-based compensation $ 15,830 $ 14,812 Stock Options We have not granted options since 2011 and all outstanding options were fully vested and associated stock-based compensation expenses was recognized as of December 31, 2015. Activity for the three months ended March 31, 2018 under the stock option plans is set forth below: Number of Shares Underlying Stock Options (in thousands) Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2017 75 $ 11.36 Exercised (15 ) 11.65 Cancelled or expired — — Outstanding as of March 31, 2018 60 $ 11.28 0.81 $ 14,369 Vested at March 31, 2018 60 $ 11.28 0.81 $ 14,369 Exercisable at March 31, 2018 60 $ 11.28 0.81 $ 14,369 Restricted Stock Units (“RSUs”) The fair value of restricted stock units (“RSUs”) is based on our closing stock price on the date of grant. A summary for the three months ended March 31, 2018 is as follows: Shares Underlying RSUs (in thousands) Weighted Average Grant Date Fair Value Weighted Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Nonvested as of December 31, 2017 1,341 $ 82.30 Granted 193 254.22 Vested and released (439 ) 67.12 Forfeited (39 ) 103.23 Nonvested as of March 31, 2018 1,056 $ 119.34 1.61 $ 265,087 As of March 31, 2018 , we expect to recognize $105.2 million of total unamortized compensation cost, net of estimated forfeitures, related to RSUs over a weighted average period of 2.5 years. Market-performance Based Restricted Stock Units (“MSUs”) On an annual basis, we grant market-performance based restricted stock units (“MSUs”) to our executive officers. Each MSU represents the right to one share of Align’s common stock. The actual number of MSUs which will be eligible to vest will be based on the performance of Align’s stock price relative to the performance of the NASDAQ Composite Index over the vesting period, generally two to three years, up to 250% of the MSUs initially granted. The following table summarizes the MSU performance for the three months ended March 31, 2018 : Number of Shares Underlying MSUs (in thousands) Weighted Average Grant Date Fair Value Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Nonvested as of December 31, 2017 428 $ 78.53 Granted 110 221.18 Vested and released (146 ) 56.75 Forfeited — — Nonvested as of March 31, 2018 392 $ 126.58 1.27 $ 98,468 As of March 31, 2018 , we expect to recognize $28.6 million of total unamortized compensation cost, net of estimated forfeitures, related to MSUs over a weighted average period of 1.3 years. Employee Stock Purchase Plan (“ESPP”) In May 2010, our shareholders approved the 2010 Employee Stock Purchase Plan (the “2010 Purchase Plan”) which will continue until terminated by either the Board of Directors or its administrator. The maximum number of shares available for purchase under the 2010 Purchase Plan is 2,400,000 shares. As of March 31, 2018 , we have 647,363 shares available for future issuance. The fair value of the option component of the 2010 Purchase Plan shares was estimated at the grant date using the Black-Scholes option pricing model with the following weighted average assumptions: Three Months Ended 2018 2017 Expected term (in years) 1.3 1.2 Expected volatility 35.7 % 26.1 % Risk-free interest rate 1.9 % 0.9 % Expected dividends — — Weighted average fair value at grant date $ 78.38 $ 26.09 As of March 31, 2018 , there was $2.4 million of total unamortized compensation costs related to employee stock purchases which we expect to be recognized over a weighted average period of 0.7 year.

Common Stock Repurchase

Common Stock Repurchase	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Common Stock Repurchase	Common Stock Repurchase April 2014 Repurchase Program In January 2017, we repurchased on the open market approximately 0.04 million shares of our common stock at an average price of $96.37 per share, including commission for an aggregate purchase price of approximately $3.8 million , completing the April 2014 Repurchase Program. April 2016 Repurchase Program On April 28, 2016, we announced that our Board of Directors had authorized a plan to repurchase up to $300.0 million of the Company’s stock (“April 2016 Repurchase Program”). In May 2017, we entered into an accelerated share repurchase agreement ("2017 ASR") to repurchase $50.0 million of our common stock. The 2017 ASR was completed in August 2017. We received a total of approximately 0.4 million shares for an average share price of $146.48 . In November 2017, we repurchased on the open market approximately 0.2 million shares of our common stock at an average price of $243.40 per share, including commissions, for an aggregate purchase price of approximately $50.0 million . In February 2018, we repurchased on the open market approximately 0.4 million shares of our common stock at an average price of $252.24 per share, including commission for an aggregate purchase price of approximately $100.0 million . As of March 31, 2018, we have $100.0 million remaining under the April 2016 Repurchase Plan.

Accounting for Income Taxes

Accounting for Income Taxes	3 Months Ended
	Mar. 31, 2018
Accounting for Income Taxes	Accounting for Income Taxes Our provision for (benefit from) income taxes was $ 2.9 million and $ (7.2) million for the three months ended March 31, 2018 and 2017 , respectively, representing effective tax rates of 2.9% and (11.4)% , respectively. As a result of the enactment of the U.S. Tax Cuts and Jobs Act (the “TCJA”), the U.S. federal statutory tax rate decreased from 35% to 21% effective January 1, 2018. Our effective tax rate differs from the statutory federal income tax rate of 21% and 35% for the three months ended March 31, 2018 and 2017 , respectively, mainly as a result of recognition of excess tax benefits related to stock-based compensation and certain foreign earnings, primarily from the Netherlands and Costa Rica, being taxed at lower tax rates. The increase in effective tax rate for the three months ended March 31, 2018 compared to the same period in 2017 is primarily attributable to the decrease in corporate tax rate from 35% to 21% pursuant to the enactment of the TCJA, which reduced the excess tax benefits related to stock-based compensation, and the benefits from foreign earnings being taxed at a lower tax rate. For the three months ended March 31, 2018 and 2017 , we recognized excess tax benefits of $23.3 million and $21.3 million , respectively, in our provision for (benefit from) income taxes. We exercise significant judgment in regards to estimates of future market growth, forecasted earnings and projected taxable income in determining the provision for income taxes and for purposes of assessing our ability to utilize any future benefit from deferred tax assets. We file U.S. federal, U.S. state, and non-U.S. income tax returns. Our major tax jurisdictions include U.S. federal, the State of California and the Netherlands. For U.S. federal and state tax returns, we are no longer subject to tax examinations for years before 2000 . With few exceptions, we are no longer subject to examination by foreign tax authorities for years before 2010 . Our total gross unrecognized tax benefits, excluding interest and penalties, was $50.3 million and $47.7 million as of March 31, 2018 and December 31, 2017 , respectively, all of which would impact our effective tax rate if recognized. Our total interest and penalties accrued as of March 31, 2018 was $3.3 million . We have elected to recognize interest and penalties related to unrecognized tax benefits as a component of income taxes. The timing and resolution of income tax examinations is uncertain, and the amounts ultimately paid, if any, upon resolution of issues raised by the taxing authorities may differ materially from the amounts accrued for each year. It is reasonably possible that the gross unrecognized tax benefits related to the years that are subject to examination could decrease, whether by payment, release, or a combination of both, in the next 12 months by $28 million , which would impact our effective tax rate. During the three months ended March 31, 2018 , we received notice that we are under examination by the Internal Revenue Service for the tax year of 2015. In June 2017, the Costa Rica Ministry of Foreign Trade, an agency of the Government of Costa Rica, granted an extension of certain income tax incentives for an additional twelve year period. Under these incentives, all of the income in Costa Rica is subject to a reduced tax rate. In order to receive the benefit of these incentives, we must hire specified numbers of employees and maintain certain minimum levels of fixed asset investment in Costa Rica. If we do not fulfill these conditions for any reason, our incentive could lapse and our income in Costa Rica would be subject to taxation at higher rates which could have a negative impact on our operating results. The Costa Rica corporate income tax rate that would apply, absent the incentives, is 30% for 2018 and 2017 . For the three months ended March 31, 2018 , the reduction in income taxes due to the reduced tax rate was minimal. As of December 31, 2017 , undistributed earnings of the Company totaled $606.5 million . We reassessed our capital needs and investment strategy with regard to the indefinite reinvestment of the undistributed earnings from certain of our foreign subsidiaries as a result of the one-time transition tax on cumulative foreign earnings under the TCJA. During the fourth quarter of 2017 , we determined that approximately $591.9 million of the total undistributed foreign earnings are no longer considered to be indefinitely reinvested outside the U.S. As a result, in the fourth quarter of 2017, we have recorded a deferred tax liability of approximately $3.3 million , which represents the provisional amount of U.S. state income taxes that would be due in the event these foreign earnings are distributed. The remaining amount of undistributed foreign earnings of approximately $14.7 million continues to be indefinitely reinvested in our international operations. Since U.S. federal income tax has already been provided under the provisions of the TCJA, the additional tax impact of the distribution of such foreign earnings to the U.S. parent would be limited to U.S. state income and withholding taxes and is not significant. As of December 31, 2017, we recorded a provisional tax charge of $84.3 million related to the one-time transition tax liability and other tax impact of the TJCA. In the first quarter of 2018, we recorded an additional provisional tax charge of $2.4 million , primarily resulting from further analysis of our cumulative foreign earnings balances affecting the transition tax liability. As we complete our analysis of the TJCA, we may make further adjustments to the provisional amounts, which may impact our provision for income taxes in the period in which the adjustments are made. The TCJA subjects a U.S. shareholder to tax on global intangible low-taxed income (“GILTI”) earned by certain foreign subsidiaries. The FASB Staff Q&A, Topic 740, No. 5, Accounting for Global Intangible Low-Taxed Income, states that an entity can make an accounting policy election to either recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years or provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only. Given the complexity of the GILTI provisions, we are still evaluating the effects of the GILTI provisions and have not yet determined our accounting policy. As of March 31, 2018, as we are still evaluating the GILTI provisions and our analysis of future taxable income that is subject to GILTI, we have included GILTI related to current-year operations only in our estimated annual effective tax rate and have not provided additional GILTI on deferred items.

Net Income Per Share

Net Income Per Share	3 Months Ended
	Mar. 31, 2018
Net Income Per Share	Net Income per Share Basic net income per share is computed using the weighted average number of shares of common stock outstanding during the period. Diluted net income per share is computed using the weighted average number of shares of common stock, adjusted for any dilutive effect of potential common stock. Potential common stock, computed using the treasury stock method, includes RSU, MSU, stock options and our ESPP. The following table sets forth the computation of basic and diluted net income per share attributable to common stock (in thousands, except per share amounts): Three Months Ended 2018 2017 Numerator: Net income $ 95,866 $ 69,420 Denominator: Weighted-average common shares outstanding, basic 80,036 79,904 Dilutive effect of potential common stock 1,592 1,630 Total shares, diluted 81,628 81,534 Net income per share, basic $ 1.20 $ 0.87 Net income per share, diluted $ 1.17 $ 0.85 For the three months ended March 31, 2018 and 2017, potentially anti-dilutive shares excluded from diluted net income per share related to RSUs, MSUs, stock options and ESPP were not material.

Segments and Geographical Infor

Segments and Geographical Information	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Segments and Geographical Information	Segments and Geographical Information Segment Information Operating segments are defined as components of an enterprise for which separate financial information is available that is evaluated regularly by the Chief Operating Decision Maker (“CODM”), or decision-making group, in deciding how to allocate resources and in assessing performance. Our CODM is our Chief Executive Officer. We report segment information based on the management approach. The management approach designates the internal reporting used by CODM for decision making and performance assessment as the basis for determining our reportable segments. The performance measures of our reportable segments include net revenues, gross profit and income from operations. Income from operations for each segment includes all geographic revenues, related cost of net revenues and operating expenses directly attributable to the segment. Certain operating expenses are attributable to operating segments and each allocation is measured differently based on the specific facts and circumstances of the costs being allocated. Costs not specifically allocated to segment income from operations include various corporate expenses such as stock-based compensation and costs related to IT, facilities, human resources, accounting and finance, legal and regulatory, and other separately managed general and administrative costs outside the operating segments. We group our operations into two reportable segments: Clear Aligner segment and Scanner segment. • Our Clear Aligner segment consists of Comprehensive Products, Non-Comprehensive Products and Non-Case revenues as defined below: • Comprehensive Products include our Invisalign Full, Teen and Assist products. • Non-Comprehensive Products include our Invisalign Express, Invisalign Lite, Invisalign i7 and Invisalign Go products in addition to revenues from the sale of aligners to SmileDirectClub (“SDC”) under our supply agreement. • Non-Case includes our Vivera retainers along with our training and ancillary products for treating malocclusion. • Our Scanner segment consists of intraoral scanning systems and additional services available with the intraoral scanners that provide digital alternatives to the traditional cast models. This segment includes our iTero scanner and OrthoCAD services. We eliminate unrealized profit on outstanding intercompany transactions. These reportable operating segments are based on how our CODM views and evaluates our operations as well as allocation of resources. The following information relates to these segments (in thousands): Three Months Ended Net revenues 2018 2017 Clear Aligner $ 385,505 $ 282,399 Scanner 51,419 27,942 Total net revenues $ 436,924 $ 310,341 Gross profit Clear Aligner $ 296,976 $ 219,947 Scanner 30,432 15,678 Total gross profit $ 327,408 $ 235,625 Income from operations Clear Aligner $ 161,454 $ 114,734 Scanner 16,082 6,004 Unallocated corporate expenses (79,344 ) (59,065 ) Total income from operations $ 98,192 $ 61,673 Depreciation and amortization Clear Aligner $ 6,384 $ 4,363 Scanner 1,104 1,037 Unallocated corporate expenses 3,946 2,467 Total depreciation and amortization $ 11,434 $ 7,867 The following table reconciles total segment income from operations in the table above to net income before provision for (benefit from) income taxes and equity losses of investee, net of tax (in thousands): Three Months Ended 2018 2017 Total segment income from operations $ 177,536 $ 120,738 Unallocated corporate expenses (79,344 ) (59,065 ) Total income from operations 98,192 61,673 Interest income 2,176 1,195 Other income (expense), net 177 450 Net income before provision for (benefit from) income taxes and equity in losses of investee $ 100,545 $ 63,318 Geographical Information Net revenues are presented below by geographic area (in thousands): Three Months Ended 2018 2017 Net revenues 1 : United States $ 237,103 $ 183,273 The Netherlands 139,531 99,799 Other International 60,290 27,269 Total net revenues $ 436,924 $ 310,341 1 Net revenues are attributed to countries based on location of where revenue is recognized. Tangible long-lived assets are presented below by geographic area (in thousands): March 31, December 31, 2017 Long-lived assets 1 : The Netherlands $ 164,165 $ 143,673 United States 126,983 128,171 Costa Rica 48,470 30,738 Mexico 30,215 25,090 China 12,258 5,480 Other International 18,437 15,641 Total long-lived assets $ 400,528 $ 348,793 1 Long-lived assets are attributed to countries based on entity that owns the assets.

Summary of Significant Accoun21

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Basis of presentation	Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements have been prepared by Align Technology, Inc. (“we”, “our”, or “Align”) in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) and contain all adjustments, including normal recurring adjustments, necessary to state fairly our results of operations for the three months ended March 31, 2018 and 2017 , our comprehensive income for the three months ended March 31, 2018 and 2017 , our financial position as of March 31, 2018 and our cash flows for the three months ended March 31, 2018 and 2017 . The Condensed Consolidated Balance Sheet as of December 31, 2017 was derived from the December 31, 2017 audited financial statements and have been recast to reflect the adoption of accounting standards as described below. It does not include all disclosures required by accounting principles generally accepted in the United States of America (“U.S.”). During the first quarter of fiscal year 2018, we adopted the Accounting Standards Codification (“ASC”) 606, “ Revenues from Contracts with Customers, ” using the full retrospective method and Accounting Standards Update (“ASU”) 2016-18, “Statement of Cash Flows - Restricted Cash,” on a retrospective basis. Condensed Consolidated Balance Sheet as of December 31, 2017 and Condensed Consolidated Statement of Cash Flow for the three months ended March 31, 2017 have been recast to comply with the adoption of these standards. The results of operations for the three months ended March 31, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 or any other future period, and we make no representations related thereto. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” “Quantitative and Qualitative Disclosures About Market Risk” and the Consolidated Financial Statements and notes thereto included in Items 7, 7A and 8, respectively, in our Annual Report on Form 10-K for the year ended December 31, 2017 .
Use of estimates	Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles (“GAAP”) in the U.S. requires our management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates. On an ongoing basis, we evaluate our estimates, including those related to the fair values of financial instruments, long-lived assets and goodwill, equity method investments, useful lives of intangible assets and property and equipment, revenue recognition, stock-based compensation, income taxes and contingent liabilities, among others. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities.
Revenue Recognition	Revenue Recognition Our revenues are derived primarily from the sale of aligners, scanners, and services from our Clear Aligner and Scanner segments. We enter into sales contracts that may consist of multiple distinct performance obligations where certain performance obligations of the sales contract are not delivered in one reporting period. We measure and allocate revenue according to Accounting Standards Codification (“ASC”) 606-10, “ Revenues from Contracts with Customers ”. We identify a performance obligation as distinct if both the following criteria are true: the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer and the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract. Determining the standalone selling price (“SSP”) and allocation of consideration from a contract to the individual performance obligations, and the appropriate timing of revenue recognition, is the result of significant qualitative and quantitative judgments. Management considers a variety of factors such as historical sales, usage rates, costs, and expected margin, which may vary over time depending upon the unique facts and circumstances related to each performance obligation in making these estimates. While changes in the allocation of the SSP between performance obligations will not affect the amount of total revenue recognized for a particular contract, any material changes could impact the timing of revenue recognition, which would have a material effect on our financial position and result of operations. This is because the contract consideration is allocated to each performance obligation, delivered or undelivered, at the inception of the contract based on the SSP of each distinct performance obligation. Clear Aligner We enter into contracts (“treatment plan(s)”) that involve multiple future performance obligations. Invisalign Full, Invisalign Teen, and Invisalign Assist products include optional additional aligners at no charge for a period of up to five years after initial shipment and Invisalign Go includes optional additional aligners at no charge for a period of up to two years after initial shipment. Invisalign Teen also includes up to six optional replacement aligners in the price of the product and may be ordered by the dental professional any time throughout treatment. Invisalign Lite includes one optional case refinement in the price of the product. Case refinement is a finishing tool used to adjust a patient’s teeth to the desired final position and may be elected by the dental professional at any time during treatment; however, it is generally ordered in the last stages of orthodontic treatment. We determined that our treatment plans comprise the following performance obligations that also represent distinct deliverables: initial aligners, additional aligners, case refinement, and replacement aligners. The Company elected to take the practical expedient to consider shipping and handling costs as activities to fulfill the performance obligation. We allocate revenue for each treatment plan based on each unit’s SSP and recognize the revenue over the manufacturing period, typically 1-3 days, as the aligners do not have an alternative use and we have enforceable rights to payment. As we collect most consideration upfront, we considered whether a significant financing component exists. However, as the delivery of the performance obligations are at the customer’s discretion, we concluded that no significant financing component exists. Scanners We sell intraoral scanners and CAD/CAM services through both our direct sales force and distribution partners. The intraoral scanner sales price includes one year of warranty and unlimited scanning services. The customer may, for additional fees, also select extended warranty and unlimited scanning services for periods beyond the initial year. When intraoral scanners are sold with an unlimited scanning service agreement and/or extended warranty, we allocate revenue based on each element’s SSP. We estimate the SSP of each element, taking into consideration historical prices as well as our discounting strategies. Revenue is then recognized over time as the monthly services are rendered and upon shipment for the scanner, as that is when we deem the customer to have obtained control. Warranties For both Clear Aligner and iTero scanner segments, the Company offers an assurance warranty, which provides the customer assurance that the product will function as the parties intended because it complies with agreed-upon specifications, and thus is not treated as a separate performance obligation and will continue to be accrued in accordance with the FASB guidance on guarantees. Volume Discounts In certain situations, we offer promotions in which the discount will increase depending upon the volume purchased over time. We concluded that in these situations, the promotions can represent either variable consideration or options, depending upon the specifics of the promotion. In the event the promotion contains an option, the option is considered a material right and therefore, included in the accounting for the initial arrangement. We estimate the average anticipated discount over the lifetime of the promotion or contract, and apply that discount to each unit as it is sold. On a quarterly basis, we review our estimates and if needed, updates are made and changes are applied prospectively. Costs to Obtain a Contract We offer a variety of commission plans to our salesforce; each plan has multiple components. To match the costs to obtain a contract to the associated revenue, we evaluate the individual components and capitalize the eligible components, recognizing the costs over the treatment period. Unfulfilled Performance Obligations for Clear Aligners and Scanners The Company’s unfilled performance obligations as of March 31, 2018 and the estimated revenue expected to be recognized in the future related to these performance obligations are $309 million . This includes performance obligations from the Clear Aligner segment, primarily the shipment of additional aligners, which are fulfilled over 1-5 years, and performance obligations from the iTero scanner segment, primarily contracted deliveries of additional scanners and support, which are fulfilled over 1-5 years. The estimate includes both product and service unfulfilled performance obligations and the time range reflect our best estimate of when the Company will transfer control to the customer and may change based on customer usage patterns, timing of shipments, readiness of customers’ facilities for installation, and manufacturing availability. Contract Balances The timing of revenue recognition results in deferred revenues on the Condensed Consolidated Balance Sheet. We usually collect the entire treatment fee prior to all performance obligations being performed and payment terms vary from net 30 to net 90. Contract liabilities are recorded as deferred revenue balances, which are generated based upon timing of invoices and recognition patterns, not payments. If the revenue recognition exceeds the billing, the exceeded amount is considered unbilled receivable and a contract asset. Conversely, if the billing occurs prior to the revenue recognition, the amount is considered deferred revenue and a contract liability.
Recent Accounting Pronouncements	Recent Accounting Pronouncements (i) New Accounting Updates Recently Adopted In May 2014, the Financial Accounting Standards Board (“FASB”) released ASU 2014-9, “ Revenue from Contracts with Customers, ” (Topic 606) to supersede nearly all existing revenue recognition guidance under GAAP. The core principle of the standard is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for the goods or services. We adopted the guidance in the first quarter of fiscal year 2018 by applying the full retrospective method. We have completed the financial statement impact of adoption including, but not limited to, volume-based discount programs, sales commissions and the identification of performance obligations. The impact of adoption was primarily related to the Clear Aligner segment. Our disaggregation of revenue can be found in Note 14 “Segments and Geographical Information.” The Company elected to take the practical expedient to exclude from the transaction price all taxes assessed by a governmental authority. In preparation for adoption of the standard, we have reviewed and, where necessary, implemented additional key system functionalities and internal controls to enable the preparation of financial information. Prior periods have been retrospectively adjusted, and we recognized cumulative effect of adopting the guidance as an adjustment to our opening balance of retained earnings as of January 1, 2016. The adoption of ASU 2014-09 did not have a material impact on our Condensed Consolidated Statements of Operations, Condensed Consolidated Statements of Comprehensive Income or Condensed Consolidated Statements of Cash Flows for the historical periods presented in the Item 1 Financial Statements section. Consolidated balance sheet line items, which reflect the adoption of the ASU 2014-09 are as follows (in thousands): December 31, 2017 As Previously Reported Adjustment As Adjusted Asset Accounts: Accounts receivable, net $ 322,825 $ 1,364 $ 324,189 Deferred tax assets 50,059 (725 ) 49,334 Other assets 38,379 5,514 43,893 Liability and Stockholders’ Equity Accounts: Accrued liabilities $ 194,198 $ 1,364 $ 195,562 Deferred revenues 266,842 871 267,713 Retained earnings 263,356 3,918 267,274 In August 2016, the FASB issued ASU 2016-15, “Classification of Certain Cash Receipts and Cash Payments,” which clarifies the presentation and classification of certain cash receipts and cash payments in the statements of cash flows. The amendments are effective for fiscal years and interim periods within those years beginning after December 15, 2017. We adopted the standard in the first quarter of fiscal year 2018 on a retrospective basis which did not have an impact on our consolidated statements of cash flows. In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows - Restricted Cash,” which provides guidance to address the classification and presentation of changes in restricted cash in the statements of cash flows . The amendments are effective for fiscal years and interim periods within those years beginning after December 15, 2017 on a retrospective basis. We adopted the guidance in the first quarter of fiscal year 2018 on a retrospective basis and presented the changes in the total of cash, cash equivalents, and restricted cash in the consolidated statements of cash flows. Consolidated statement of cash flows line items, which reflect the adoption of the ASU 2016-18, are as follows (in thousands): March 31, 2017 As Previously Reported Adjustment As Adjusted Cash Flows from Investing Activities Other investing activities $ 2,314 $ (3,164 ) $ (850 ) Net cash provided by (used in) investing activities (145,298 ) (3,164 ) (148,462 ) Net increase (decrease) in cash, cash equivalent, and restricted cash (128,248 ) (3,164 ) (131,412 ) Cash, cash equivalents, and restricted cash at beginning of the period 389,275 3,744 393,019 Cash, cash equivalents, and restricted cash at end of the period $ 261,027 $ 580 $ 261,607 In May 2017, the FASB issued ASU 2017-09, “ Compensation — Stock Compensation (Topic 718): Scope of Modification Accounting,” to clarify when to account for a change to the terms or conditions of a share-based payment award as a modification. The amendments are effective for fiscal years and interim periods within those years beginning after December 15, 2017 on a prospective basis. We adopted the standard in the first quarter of fiscal year 2018 on a prospective basis which did not have an impact on our consolidated financial statements and related disclosures. (ii) Recent Accounting Updates Not Yet Effective In February 2016, the FASB issued ASU 2016-02, “ Leases ” (Topic 842) to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The updated guidance is effective for annual periods beginning after December 15, 2018, including interim periods within those fiscal years. We plan to adopt the standard in the first quarter of fiscal year 2019 by electing practical expedients available in the standard. While we are currently evaluating the impact of the adoption of this guidance on our consolidated financial statements, we expect the adoption will have a material increase in assets and liabilities on our consolidated balance sheet. In June 2016, the FASB issued ASU 2016-13, “ Financial Instruments - Credit Losses ” (Topic 326) . The FASB issued this update to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. The amendments in this update replace the existing guidance of incurred loss impairment methodology with an approach that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The updated guidance is effective for annual periods beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption of the update is permitted in fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. We are currently evaluating the impact of this guidance on our consolidated financial statements and related disclosures. In January 2017, the FASB issued ASU 2017-04, “Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment,” to simplify the subsequent measurement of goodwill by eliminating step two from the goodwill impairment test. Under the amendments, an entity will recognize an impairment charge for the amount by which the carrying value exceeds the fair value. The amendments are effective for fiscal years and interim periods within those years beginning after December 15, 2019 on a prospective basis and early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements and related disclosures. In February 2018, the FASB issued ASU 2018-02, “Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income,” which gives entities the option to reclassify to retained earnings the tax effects resulting from the U.S. Tax Cuts and Jobs Act (the “TCJA”) related to items in accumulated other comprehensive income. The amendments are effective for fiscal years and interim periods within those years beginning after December 15, 2018 on a retrospective basis and early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements and related disclosures.

Summary of Significant Accoun22

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	Consolidated statement of cash flows line items, which reflect the adoption of the ASU 2016-18, are as follows (in thousands): March 31, 2017 As Previously Reported Adjustment As Adjusted Cash Flows from Investing Activities Other investing activities $ 2,314 $ (3,164 ) $ (850 ) Net cash provided by (used in) investing activities (145,298 ) (3,164 ) (148,462 ) Net increase (decrease) in cash, cash equivalent, and restricted cash (128,248 ) (3,164 ) (131,412 ) Cash, cash equivalents, and restricted cash at beginning of the period 389,275 3,744 393,019 Cash, cash equivalents, and restricted cash at end of the period $ 261,027 $ 580 $ 261,607 Consolidated balance sheet line items, which reflect the adoption of the ASU 2014-09 are as follows (in thousands): December 31, 2017 As Previously Reported Adjustment As Adjusted Asset Accounts: Accounts receivable, net $ 322,825 $ 1,364 $ 324,189 Deferred tax assets 50,059 (725 ) 49,334 Other assets 38,379 5,514 43,893 Liability and Stockholders’ Equity Accounts: Accrued liabilities $ 194,198 $ 1,364 $ 195,562 Deferred revenues 266,842 871 267,713 Retained earnings 263,356 3,918 267,274

Marketable Securities and Fai23

Marketable Securities and Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Short-Term And Long-Term Marketable Securities	As of March 31, 2018 and December 31, 2017, the estimated fair value of our short-term and long-term marketable securities, classified as available for sale, are as follows (in thousands): Short-term March 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Commercial paper $ 20,447 $ — $ (1 ) $ 20,446 Corporate bonds 106,583 1 (333 ) 106,251 U.S. government agency bonds 8,999 — (52 ) 8,947 U.S. government treasury bonds 28,146 — (51 ) 28,095 Certificates of deposit 1,001 — — 1,001 Total marketable securities, short-term $ 165,176 $ 1 $ (437 ) $ 164,740 Long-term March 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. government agency bonds $ 7,032 $ — $ (66 ) $ 6,966 Corporate bonds 3,265 1 (20 ) 3,246 Total marketable securities, long-term $ 10,297 $ 1 $ (86 ) $ 10,212 Short-term December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Commercial paper $ 58,503 $ — $ (1 ) $ 58,502 Corporate bonds 145,728 3 (174 ) 145,557 U.S. government agency bonds 3,013 — (7 ) 3,006 U.S. government treasury bonds 60,650 — (70 ) 60,580 Certificates of deposit 4,386 — — 4,386 Total marketable securities, short-term $ 272,280 $ 3 $ (252 ) $ 272,031 Long-term December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. government agency bonds $ 15,023 $ — $ (68 ) $ 14,955 Corporate bonds 25,067 2 (76 ) 24,993 Total marketable securities, long-term $ 40,090 $ 2 $ (144 ) $ 39,948
Investments Classified by Contractual Maturity Date	As the carrying value approximates the fair value for our short-term and long-term marketable securities shown in the tables above, the following table summarizes the fair value of our short-term and long-term marketable securities classified by maturity as of March 31, 2018 and December 31, 2017 (in thousands): March 31, 2018 December 31, 2017 One year or less $ 164,740 $ 272,031 Due in greater than one year 10,212 39,948 Total available for sale short-term and long-term marketable securities $ 174,952 $ 311,979
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	The following table summarizes the reconciliation of assets measured and recorded at fair value on a recurring basis using significant unobservable inputs Level 3 (in thousands): Notes Receivable Balance as of December 31, 2017 $ 4,476 Accrued interest receivable 25 Change in fair value recognized in earnings 358 Balance as of March 31, 2018 $ 4,859
Financial Assets Measured At Fair Value On Recurring Basis	The following tables summarize our financial assets measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017 (in thousands): Description Balance as of March 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Other Cash equivalents: Money market funds $ 255,373 $ 255,373 $ — $ — Short-term investments: Commercial paper 20,446 — 20,446 — Corporate bonds 106,251 — 106,251 — U.S. government agency bonds 8,947 — 8,947 — U.S. government treasury bonds 28,095 28,095 — — Certificates of deposit 1,001 — 1,001 — Long-term investments: U.S. government agency bonds 6,966 — 6,966 — Corporate bonds 3,246 — 3,246 — Prepaid expenses and other current assets: Israeli funds 3,114 — 3,114 — Short-term notes receivable 4,859 — — 4,859 $ 438,298 $ 283,468 $ 149,971 $ 4,859 Description Balance as of December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Other Cash equivalents: Money market funds $ 253,155 $ 253,155 $ — $ — Commercial paper 7,246 — 7,246 — Corporate bonds 2,016 — 2,016 — Short-term investments: Commercial paper 58,502 — 58,502 — Corporate bonds 145,557 — 145,557 — U.S. government agency bonds 3,006 — 3,006 — U.S. government treasury bonds 60,580 60,580 — — Certificates of deposit 4,386 — 4,386 — Long-term investments: U.S. government agency bonds 14,955 — 14,955 — Corporate bonds 24,993 — 24,993 — Prepaid expenses and other current assets: Israeli funds 3,075 — 3,075 — Short-term notes receivable 4,476 — — 4,476 $ 581,947 $ 313,735 $ 263,736 $ 4,476
Notional value of derivative instruments	The following table presents the gross notional value of all our foreign exchange forward contracts outstanding as of March 31, 2018 (in thousands): March 31, 2018 Local Currency Amount Notional Contract Amount (USD) Euro €40,000 $ 49,244 British Pound £9,000 12,615 $ 61,859

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Schedule of Inventories	Inventories consist of the following (in thousands): March 31, December 31, Raw materials $ 13,386 $ 12,721 Work in process 11,442 12,157 Finished goods 11,038 6,810 Total inventories $ 35,866 $ 31,688
Schedule of Other Assets	Other assets consist of the following (in thousands): March 31, December 31, Capitalized commissions $ 7,681 $ 5,515 Other long-term assets 5,831 4,821 Security deposits 3,721 3,557 Loan receivable — 30,000 Total other assets $ 17,233 $ 43,893
Schedule of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): March 31, December 31, Accrued payroll and benefits $ 69,581 $ 103,004 Accrued expenses 32,458 27,318 Accrued income taxes 17,134 12,405 Accrued fixed assets 15,241 11,362 Accrued warranty 6,657 5,929 Accrued professional fees 6,562 6,316 Accrued sales tax and value added tax 5,340 5,503 Accrued sales rebate 5,121 11,209 Accrued sales return reserve 1 4,887 1,364 Other accrued liabilities 17,112 11,152 Total accrued liabilities $ 180,093 $ 195,562 1 December 31, 2017 balance has been reclassified from accounts receivable, net to reflect the adoption of ASU 2014-09 ( Refer to Note 1 “Summary of Significant Accounting Policies” of the Notes to Condensed Consolidated Financial Statements for more information).
Schedule of Warranty Accrual	Warranty accrual as of March 31, 2018 and 2017 consists of the following activity (in thousands): Three Months Ended 2018 2017 Balance at beginning of period $ 5,929 $ 3,841 Charged to cost of revenues 2,359 1,822 Actual warranty expenditures (1,631 ) (1,362 ) Balance at end of period $ 6,657 $ 4,301
Schedule of Deferred Revenues	Deferred revenues consist of the following (in thousands): March 31, December 31, Deferred revenues - current $ 296,011 $ 267,713 Deferred revenues - long-term 1 6,171 4,588 1 Included in other long-term liabilities on our Condensed Consolidated Balance Sheets

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Summary of Goodwill by Reportable Segment	The change in the carrying value of goodwill for the three months ended March 31, 2018 , all attributable to our Clear Aligner reporting unit, is as follows (in thousands): Total Balance as of December 31, 2017 $ 64,614 Adjustments 1 7 Balance as of March 31, 2018 $ 64,621 1 The adjustments to goodwill during the period were a result of foreign currency translation.
Schedule of Amortized Intangible Assets	Acquired intangible long-lived assets are being amortized as follows (in thousands): Weighted Average Amortization Period (in years) Gross Carrying Amount as of Accumulated Amortization Accumulated Impairment Loss Net Carrying Trademarks 15 $ 7,100 $ (1,803 ) $ (4,179 ) $ 1,118 Existing technology 13 12,600 (4,845 ) (4,328 ) 3,427 Customer relationships 11 33,500 (15,147 ) (10,751 ) 7,602 Reacquired rights 3 7,500 (1,914 ) — 5,586 Patents 8 6,796 (1,712 ) — 5,084 Other 2 618 (427 ) — 191 Total intangible assets $ 68,114 $ (25,848 ) $ (19,258 ) $ 23,008 Weighted Average Amortization Period (in years) Gross Carrying Amount as of December 31, 2017 Accumulated Amortization Accumulated Impairment Loss Net Carrying Value as of December 31, 2017 Trademarks 15 $ 7,100 $ (1,769 ) $ (4,179 ) $ 1,152 Existing technology 13 12,600 (4,704 ) (4,328 ) 3,568 Customer relationships 11 33,500 (14,681 ) (10,751 ) 8,068 Reacquired rights 3 7,500 (1,356 ) — 6,144 Patents 8 6,798 (1,504 ) — 5,294 Other 2 618 (390 ) — 228 Total intangible assets $ 68,116 $ (24,404 ) $ (19,258 ) $ 24,454
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	The total estimated annual future amortization expense for these acquired intangible assets as of March 31, 2018 is as follows (in thousands): Fiscal Year Ending December 31, Remainder of 2018 $ 4,843 2019 6,343 2020 3,882 2021 3,389 2022 2,116 Thereafter 2,435 Total $ 23,008

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Schedule of Future Lease Payments	As of March 31, 2018 , minimum future lease payments for non-cancelable operating leases are as follows (in thousands): Fiscal Year Ending December 31, Operating Leases Remainder of 2018 $ 13,508 2019 15,061 2020 11,056 2021 9,270 2022 7,107 Thereafter 10,537 Total minimum future lease payments $ 66,539

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Stock-based Compensation Expense	The stock-based compensation related to all of our stock-based awards and employee stock purchases for the three months ended March 31, 2018 and 2017 is as follows (in thousands): Three Months Ended 2018 2017 Cost of net revenues $ 881 $ 925 Selling, general and administrative 12,578 11,716 Research and development 2,371 2,171 Total stock-based compensation $ 15,830 $ 14,812
Stock Option Activity	Activity for the three months ended March 31, 2018 under the stock option plans is set forth below: Number of Shares Underlying Stock Options (in thousands) Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2017 75 $ 11.36 Exercised (15 ) 11.65 Cancelled or expired — — Outstanding as of March 31, 2018 60 $ 11.28 0.81 $ 14,369 Vested at March 31, 2018 60 $ 11.28 0.81 $ 14,369 Exercisable at March 31, 2018 60 $ 11.28 0.81 $ 14,369
Summary Of Restricted Stock Units	A summary for the three months ended March 31, 2018 is as follows: Shares Underlying RSUs (in thousands) Weighted Average Grant Date Fair Value Weighted Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Nonvested as of December 31, 2017 1,341 $ 82.30 Granted 193 254.22 Vested and released (439 ) 67.12 Forfeited (39 ) 103.23 Nonvested as of March 31, 2018 1,056 $ 119.34 1.61 $ 265,087
Summary Of Market-performance Based Restricted Stock Units	The following table summarizes the MSU performance for the three months ended March 31, 2018 : Number of Shares Underlying MSUs (in thousands) Weighted Average Grant Date Fair Value Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Nonvested as of December 31, 2017 428 $ 78.53 Granted 110 221.18 Vested and released (146 ) 56.75 Forfeited — — Nonvested as of March 31, 2018 392 $ 126.58 1.27 $ 98,468
Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions	The fair value of the option component of the 2010 Purchase Plan shares was estimated at the grant date using the Black-Scholes option pricing model with the following weighted average assumptions: Three Months Ended 2018 2017 Expected term (in years) 1.3 1.2 Expected volatility 35.7 % 26.1 % Risk-free interest rate 1.9 % 0.9 % Expected dividends — — Weighted average fair value at grant date $ 78.38 $ 26.09

Net Income Per Share (Tables)

Net Income Per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Schedule Of Earnings Per Share Basic And Diluted	The following table sets forth the computation of basic and diluted net income per share attributable to common stock (in thousands, except per share amounts): Three Months Ended 2018 2017 Numerator: Net income $ 95,866 $ 69,420 Denominator: Weighted-average common shares outstanding, basic 80,036 79,904 Dilutive effect of potential common stock 1,592 1,630 Total shares, diluted 81,628 81,534 Net income per share, basic $ 1.20 $ 0.87 Net income per share, diluted $ 1.17 $ 0.85

Segments and Geographical Inf29

Segments and Geographical Information (Tables)	3 Months Ended
	Mar. 31, 2018
Notes To Financial Statements [Abstract]
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas	These reportable operating segments are based on how our CODM views and evaluates our operations as well as allocation of resources. The following information relates to these segments (in thousands): Three Months Ended Net revenues 2018 2017 Clear Aligner $ 385,505 $ 282,399 Scanner 51,419 27,942 Total net revenues $ 436,924 $ 310,341 Gross profit Clear Aligner $ 296,976 $ 219,947 Scanner 30,432 15,678 Total gross profit $ 327,408 $ 235,625 Income from operations Clear Aligner $ 161,454 $ 114,734 Scanner 16,082 6,004 Unallocated corporate expenses (79,344 ) (59,065 ) Total income from operations $ 98,192 $ 61,673 Depreciation and amortization Clear Aligner $ 6,384 $ 4,363 Scanner 1,104 1,037 Unallocated corporate expenses 3,946 2,467 Total depreciation and amortization $ 11,434 $ 7,867 The following table reconciles total segment income from operations in the table above to net income before provision for (benefit from) income taxes and equity losses of investee, net of tax (in thousands): Three Months Ended 2018 2017 Total segment income from operations $ 177,536 $ 120,738 Unallocated corporate expenses (79,344 ) (59,065 ) Total income from operations 98,192 61,673 Interest income 2,176 1,195 Other income (expense), net 177 450 Net income before provision for (benefit from) income taxes and equity in losses of investee $ 100,545 $ 63,318 Geographical Information Net revenues are presented below by geographic area (in thousands): Three Months Ended 2018 2017 Net revenues 1 : United States $ 237,103 $ 183,273 The Netherlands 139,531 99,799 Other International 60,290 27,269 Total net revenues $ 436,924 $ 310,341 1 Net revenues are attributed to countries based on location of where revenue is recognized. Tangible long-lived assets are presented below by geographic area (in thousands): March 31, December 31, 2017 Long-lived assets 1 : The Netherlands $ 164,165 $ 143,673 United States 126,983 128,171 Costa Rica 48,470 30,738 Mexico 30,215 25,090 China 12,258 5,480 Other International 18,437 15,641 Total long-lived assets $ 400,528 $ 348,793 1 Long-lived assets are attributed to countries based on entity that owns the assets.

Summary of Significant Accoun30

Summary of Significant Accounting Policies - Narrative (Details) $ in Millions	Mar. 31, 2018USD ($)
Notes To Financial Statements [Abstract]
Revenue remaining performance obligation	$ 309

Summary of Significant Accoun31

Summary of Significant Accounting Policies - Balance sheet as adjusted (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 361,459	$ 324,189
Deferred tax assets	45,524	49,334
Other assets		43,893
Accrued liabilities	180,093	195,562
Deferred revenues	296,011	267,713
Retained earnings	$ 267,336	267,274
As Previously Reported | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net		322,825
Deferred tax assets		50,059
Other assets		38,379
Accrued liabilities		194,198
Deferred revenues		266,842
Retained earnings		263,356
Adjustment | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net		1,364
Deferred tax assets		(725)
Other assets		5,514
Accrued liabilities		1,364
Deferred revenues		871
Retained earnings		$ 3,918

Summary of Significant Accoun32

Summary of Significant Accounting Policies - Cash flow statement as adjusted (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Initial Application Period [Line Items]
Other investing activities	$ 462	$ (850)
Net cash provided by (used in) investing activities	109,269	(148,462)
Net increase (decrease) in cash, cash equivalent, and restricted cash		(131,412)
Cash, cash equivalents, and restricted cash at beginning of the period	450,125	393,019
Cash, cash equivalents, and restricted cash at end of the period	$ 498,619	261,607
As Previously Reported
Initial Application Period [Line Items]
Other investing activities		2,314
Net cash provided by (used in) investing activities		(145,298)
Net increase (decrease) in cash, cash equivalent, and restricted cash		(128,248)
Cash, cash equivalents, and restricted cash at beginning of the period		389,275
Cash, cash equivalents, and restricted cash at end of the period		261,027
Accounting Standards Update 2016-18 | Adjustment
Initial Application Period [Line Items]
Other investing activities		(3,164)
Net cash provided by (used in) investing activities		(3,164)
Net increase (decrease) in cash, cash equivalent, and restricted cash		(3,164)
Cash, cash equivalents, and restricted cash at beginning of the period		3,744
Cash, cash equivalents, and restricted cash at end of the period		$ 580

Short-Term and Long-Term Market

Short-Term and Long-Term Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Total available for sale short-term and long-term marketable securities	$ 174,952	$ 311,979
Fair Value, Measurements, Recurring | Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	165,176	272,280
Gross Unrealized Gains	1	3
Gross Unrealized Losses	(437)	(252)
Total available for sale short-term and long-term marketable securities	164,740	272,031
Fair Value, Measurements, Recurring | Short-term Investments | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,447	58,503
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(1)
Total available for sale short-term and long-term marketable securities	20,446	58,502
Fair Value, Measurements, Recurring | Short-term Investments | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	106,583	145,728
Gross Unrealized Gains	1	3
Gross Unrealized Losses	(333)	(174)
Total available for sale short-term and long-term marketable securities	106,251	145,557
Fair Value, Measurements, Recurring | Short-term Investments | U.S. government agency bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,999	3,013
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(52)	(7)
Total available for sale short-term and long-term marketable securities	8,947	3,006
Fair Value, Measurements, Recurring | Short-term Investments | U.S. government treasury bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	28,146	60,650
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(51)	(70)
Total available for sale short-term and long-term marketable securities	28,095	60,580
Fair Value, Measurements, Recurring | Short-term Investments | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,001	4,386
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Total available for sale short-term and long-term marketable securities	1,001	4,386
Fair Value, Measurements, Recurring | Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,297	40,090
Gross Unrealized Gains	1	2
Gross Unrealized Losses	(86)	(144)
Total available for sale short-term and long-term marketable securities	10,212	39,948
Fair Value, Measurements, Recurring | Long-term Investments | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,265	25,067
Gross Unrealized Gains	1	2
Gross Unrealized Losses	(20)	(76)
Total available for sale short-term and long-term marketable securities	3,246	24,993
Fair Value, Measurements, Recurring | Long-term Investments | U.S. government agency bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,032	15,023
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(66)	(68)
Total available for sale short-term and long-term marketable securities	$ 6,966	$ 14,955

Marketable Securities and Fai34

Marketable Securities and Fair Value Measurements Additional Information (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Original maturity of highly liquid investments included in cash and cash equivalents	40 months
Weighted average maturity	5 months	6 months

Marketable Securities and Fai35

Marketable Securities and Fair Value Measurements Available For Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
One year or less	$ 164,740	$ 272,031
Due in greater than one year	10,212	39,948
Total available for sale short-term and long-term marketable securities	$ 174,952	$ 311,979

Marketable Securities and Fai36

Marketable Securities and Fair Value Measurements - Reconciliation (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance as of December 31, 2017	$ 4,476
Accrued interest receivable	25
Change in fair value recognized in earnings	358
Balance as of March 31, 2018	$ 4,859

Summary of Financial Assets Mea

Summary of Financial Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	$ 174,952	$ 311,979
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets, Fair Value Disclosure	438,298	581,947
Fair Value, Measurements, Recurring | Prepaid expenses and other current assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other assets	3,114	3,075
Fair Value, Measurements, Recurring | Short-term notes receivable
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term notes receivable	4,859	4,476
Fair Value, Measurements, Recurring | Cash Equivalents | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	255,373	253,155
Fair Value, Measurements, Recurring | Cash Equivalents | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents		7,246
Fair Value, Measurements, Recurring | Cash Equivalents | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents		2,016
Fair Value, Measurements, Recurring | Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	164,740	272,031
Fair Value, Measurements, Recurring | Short-term Investments | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	20,446	58,502
Fair Value, Measurements, Recurring | Short-term Investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	106,251	145,557
Fair Value, Measurements, Recurring | Short-term Investments | U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	8,947	3,006
Fair Value, Measurements, Recurring | Short-term Investments | U.S. government treasury bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	28,095	60,580
Fair Value, Measurements, Recurring | Short-term Investments | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	1,001	4,386
Fair Value, Measurements, Recurring | Long-term Investments
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	10,212	39,948
Fair Value, Measurements, Recurring | Long-term Investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	3,246	24,993
Fair Value, Measurements, Recurring | Long-term Investments | U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	6,966	14,955
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets, Fair Value Disclosure	283,468	313,735
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Prepaid expenses and other current assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other assets	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term notes receivable
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term notes receivable	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash Equivalents | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	255,373	253,155
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash Equivalents | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents		0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash Equivalents | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents		0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments | U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments | U.S. government treasury bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	28,095	60,580
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Investments | U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets, Fair Value Disclosure	149,971	263,736
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Prepaid expenses and other current assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other assets	3,114	3,075
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Short-term notes receivable
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term notes receivable	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Cash Equivalents | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Cash Equivalents | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents		7,246
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Cash Equivalents | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents		2,016
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Short-term Investments | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	20,446	58,502
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Short-term Investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	106,251	145,557
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Short-term Investments | U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	8,947	3,006
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Short-term Investments | U.S. government treasury bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Short-term Investments | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	1,001	4,386
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Long-term Investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	3,246	24,993
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Long-term Investments | U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	6,966	14,955
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets, Fair Value Disclosure	4,859	4,476
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3) | Prepaid expenses and other current assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other assets	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3) | Short-term notes receivable
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term notes receivable	4,859	4,476
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3) | Cash Equivalents | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3) | Cash Equivalents | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents		0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3) | Cash Equivalents | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents		0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3) | Short-term Investments | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3) | Short-term Investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3) | Short-term Investments | U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3) | Short-term Investments | U.S. government treasury bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3) | Short-term Investments | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3) | Long-term Investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 3) | Long-term Investments | U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments	$ 0	$ 0

Marketable Securities and Fai38

Marketable Securities and Fair Value Measurements - Derivative Notional Instruments (Details) - Mar. 31, 2018 - Significant Other Observable Inputs (Level 2) - Prepaid expenses and other current assets - Foreign Exchange Forward € in Thousands, £ in Thousands, $ in Thousands	EUR (€)	USD ($)	GBP (£)
Derivative [Line Items]
Notional amount		$ 61,859
Euro
Derivative [Line Items]
Notional amount	€ 40,000	49,244
British Pound
Derivative [Line Items]
Notional amount		$ 12,615	£ 9,000

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Disclosure Inventories [Abstract]
Raw materials	$ 13,386	$ 12,721
Work in process	11,442	12,157
Finished goods	11,038	6,810
Total inventories	$ 35,866	$ 31,688

Balance Sheet Components Other

Balance Sheet Components Other Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Notes To Financial Statements [Abstract]
Capitalized commissions	$ 7,681	$ 5,515
Other long-term assets	5,831	4,821
Security deposits	3,721	3,557
Loan receivable	0	30,000
Total other assets	$ 17,233	$ 43,893

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Disclosure Accrued Liabilities [Abstract]
Accrued payroll and benefits	$ 69,581	$ 103,004
Accrued expenses	32,458	27,318
Accrued income taxes	17,134	12,405
Accrued fixed assets	15,241	11,362
Accrued warranty	6,657	5,929
Accrued professional fees	6,562	6,316
Accrued sales tax and value added tax	5,340	5,503
Accrued sales rebate	5,121	11,209
Accrued sales return reserve	4,887	1,364
Other accrued liabilities	17,112	11,152
Total accrued liabilities	$ 180,093	$ 195,562

Warranty Accrual Activity (Deta

Warranty Accrual Activity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 5,929	$ 3,841
Charged to cost of revenues	2,359	1,822
Actual warranty expenditures	(1,631)	(1,362)
Balance at end of period	$ 6,657	$ 4,301

Balance Sheet Components Deferr

Balance Sheet Components Deferred Revenues (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Notes To Financial Statements [Abstract]
Deferred revenues - current	$ 296,011	$ 267,713
Deferred revenues - long-term	$ 6,171	$ 4,588

Balance Sheet Components - Narr

Balance Sheet Components - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Condensed Balance Sheet Statements, Captions [Line Items]
Deferred revenues	$ 436,924		$ 310,341
Deferred Revenue
Condensed Balance Sheet Statements, Captions [Line Items]
Deferred revenues		$ 86,000		$ 51,000

Equity Method Investments (Deta

Equity Method Investments (Details) - USD ($) $ in Thousands	Jul. 24, 2017	Jul. 25, 2016	Mar. 31, 2018	Mar. 31, 2017	Feb. 07, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Equity method investments			$ 52,829			$ 54,606
Net revenues			436,924	$ 310,341
SDC
Schedule of Equity Method Investments [Line Items]
Ownership	19.00%	17.00%
Payments to acquire	$ 12,800	$ 46,700
Additional ownership acquired	2.00%
Due from related parties			8,100			$ 14,300
Net revenues			$ 5,300	$ 600
Loan receivable		$ 30,000			$ 30,000

Business Combinations (Details)

Business Combinations (Details) - Certain Distributors $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)
Business Acquisition [Line Items]
Cash consideration	$ 9.5
Net tangible liabilities	1.9
Intangibles acquired	8.2
Goodwill and intangible assets, net	$ 3.2

Goodwill and Intangible Asset47

Goodwill and Intangible Assets - Change in Carrying Value of Goodwill (Details) - Clear Aligner $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Goodwill [Roll Forward]
Balance as of December 31, 2017	$ 64,614
Adjustments	7
Balance as of March 31, 2018	$ 64,621

Goodwill and Intangible Asset48

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount, beginning balance	$ 68,114	$ 68,116
Accumulated Amortization	(25,848)	(24,404)
Accumulated Impairment Loss	(19,258)	(19,258)
Net Carrying Value, ending balance	$ 23,008	$ 24,454
Trademarks
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	15 years	15 years
Gross Carrying Amount, beginning balance	$ 7,100	$ 7,100
Accumulated Amortization	(1,803)	(1,769)
Accumulated Impairment Loss	(4,179)	(4,179)
Net Carrying Value, ending balance	$ 1,118	$ 1,152
Existing technology
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	13 years	13 years
Gross Carrying Amount, beginning balance	$ 12,600	$ 12,600
Accumulated Amortization	(4,845)	(4,704)
Accumulated Impairment Loss	(4,328)	(4,328)
Net Carrying Value, ending balance	$ 3,427	$ 3,568
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	11 years	11 years
Gross Carrying Amount, beginning balance	$ 33,500	$ 33,500
Accumulated Amortization	(15,147)	(14,681)
Accumulated Impairment Loss	(10,751)	(10,751)
Net Carrying Value, ending balance	$ 7,602	$ 8,068
Reacquired rights
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	3 years	3 years
Gross Carrying Amount, beginning balance	$ 7,500	$ 7,500
Accumulated Amortization	(1,914)	(1,356)
Accumulated Impairment Loss	0	0
Net Carrying Value, ending balance	$ 5,586	$ 6,144
Patents
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	8 years	8 years
Gross Carrying Amount, beginning balance	$ 6,796	$ 6,798
Accumulated Amortization	(1,712)	(1,504)
Accumulated Impairment Loss	0	0
Net Carrying Value, ending balance	$ 5,084	$ 5,294
Other
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	2 years	2 years
Gross Carrying Amount, beginning balance	$ 618	$ 618
Accumulated Amortization	(427)	(390)
Accumulated Impairment Loss	0	0
Net Carrying Value, ending balance	$ 191	$ 228

Goodwill and Intangible Asset49

Goodwill and Intangible Assets - Total Estimated Annual Future Amortization Expense for Acquired Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Disclosure Total Estimated Annual Future Amortization Expense For Acquired Intangible Assets [Abstract]
Remainder of 2018	$ 4,843
2,019	6,343
2,020	3,882
2,021	3,389
2,022	2,116
Thereafter	2,435
Net Carrying Value, ending balance	$ 23,008	$ 24,454

Goodwill and Intangible Asset50

Goodwill and Intangible Assets - Narrative (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill impairment			$ 0
Amortization	$ 1,400,000	$ 1,400,000

Credit Facilities - Additional

Credit Facilities - Additional Information (Details) - USD ($)	Feb. 27, 2018	Mar. 31, 2018	Mar. 22, 2013
Line of Credit Facility [Line Items]
Line of credit, available borrowings	$ 200,000,000		$ 50,000,000
Current borrowing capacity	$ 50,000,000		$ 10,000,000
Outstanding borrowings		$ 0
Base Rate
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate	0.50%
London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate	1.00%
Minimum | Base Rate
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate	0.25%
Minimum | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate	1.25%
Maximum | Base Rate
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate	0.75%
Maximum | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate	1.75%

Legal Proceedings - Narrative (

Legal Proceedings - Narrative (Details)	Nov. 14, 2017Lawsuitpatent
Lawsuit Against 3Shape AS
Loss Contingencies [Line Items]
Number of lawsuits/complaints	6
Patents Allegedly Infringed upon | patent	26
Violation Of Trade Laws 3Shape
Loss Contingencies [Line Items]
Number of lawsuits/complaints	2
Patent Infringement By 3Shape
Loss Contingencies [Line Items]
Number of lawsuits/complaints	4

Commitments and Contingencies M

Commitments and Contingencies Minimum Future Lease Payments for Non-Cancelable Leases (Details) - USD ($)	Jul. 25, 2016	Mar. 31, 2018
Disclosure Minimum Future Lease Payments For Non Cancelable Leases [Abstract]
Remainder of 2018		$ 13,508,000
2,019		15,061,000
2,020		11,056,000
2,021		9,270,000
2,022		7,107,000
Thereafter		10,537,000
Total minimum lease payments		$ 66,539,000
Maximum | SDC
Other Commitments [Line Items]
Loan facility	$ 30,000,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)shares
Incentive Plan 2005
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance	27,783,379
Number of shares available for issuance	6,302,917
Employee Stock Purchase Plan 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares available	2,400,000
Number of shares remaining	647,363
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unamortized compensation cost | $	$ 105.2
Weighted average period of total unamortized cost (in years)	2 years 6 months
Market Performance Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unamortized compensation cost | $	$ 28.6
Weighted average period of total unamortized cost (in years)	1 year 3 months
Market Performance Based Restricted Stock Units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of granted market-performance based restricted stock units	2 years
Market Performance Based Restricted Stock Units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of granted market-performance based restricted stock units	3 years
Percentage of market-performance based restricted stock units eligible to vest over the vesting period	250.00%
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unamortized compensation cost | $	$ 2.4
Weighted average period of total unamortized cost (in years)	8 months

Stockholders' Equity - Stock-Ba

Stockholders' Equity - Stock-Based Compensation Expense Related to All Stock-Based Awards and Employee Stock Purchases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 15,830	$ 14,812
Cost of net revenues
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	881	925
Selling, general and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	12,578	11,716
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,371	$ 2,171

Stockholders' Equity - Activity

Stockholders' Equity - Activity Under Stock Option Plans (Details) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)$ / sharesshares
Number of Shares Underlying Stock Options
Outstanding as of December 31, 2017 | shares	75
Exercised | shares	(15)
Cancelled or expired | shares	0
Outstanding as of March 31, 2018 | shares	60
Vested at March 31, 2018 | shares	60
Exercisable at March 31, 2018 | shares	60
Weighted Average Exercise Price per Share
Outstanding as of December 31, 2017 | $ / shares	$ 11.36
Exercised | $ / shares	11.65
Cancelled or expired | $ / shares	0
Outstanding as of March 31, 2018 | $ / shares	11.28
Vested at March 31, 2018 | $ / shares	11.28
Exercisable at March 31, 2018 | $ / shares	$ 11.28
Weighted Average Remaining Contractual Term
Outstanding as of March 31, 2018	9 months 22 days
Vested at March 31, 2018	9 months 22 days
Exercisable at March 31, 2018	9 months 22 days
Aggregate Intrinsic Value
Outstanding as of March 31, 2018 | $	$ 14,369
Vested at March 31, 2018 | $	14,369
Exercisable at March 31, 2018 | $	$ 14,369

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Nonvested Shares (Details) - Restricted Stock Units (RSUs) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)$ / sharesshares
Number of Shares Underlying RSUs
Nonvested as of December 31, 2017 | shares	1,341
Granted | shares	193
Vested and released | shares	(439)
Forfeited | shares	(39)
Nonvested as of March 31, 2018 | shares	1,056
Weighted Average Grant Date Fair Value
Nonvested as of December 31, 2017 | $ / shares	$ 82.30
Granted | $ / shares	254.22
Vested and released | $ / shares	67.12
Forfeited | $ / shares	103.23
Nonvested as of March 31, 2018 | $ / shares	$ 119.34
Weighted Remaining Contractual Term (in years)
Nonvested as of March 31, 2018	1 year 7 months 10 days
Aggregate Intrinsic Value
Nonvested as of March 31, 2018 | $	$ 265,087

Stockholders' Equity - Summar58

Stockholders' Equity - Summary of MSU Performance (Details) - Market Performance Based Restricted Stock Units $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)$ / sharesshares
Number of Shares Underlying MSUs
Nonvested as of December 31, 2017 | shares	428
Granted | shares	110
Vested and released | shares	(146)
Forfeited | shares	0
Nonvested as of March 31, 2018 | shares	392
Weighted Average Grant Date Fair Value
Nonvested as of December 31, 2017 | $ / shares	$ 78.53
Granted | $ / shares	221.18
Vested and released | $ / shares	56.75
Forfeited | $ / shares	0
Nonvested as of March 31, 2018 | $ / shares	$ 126.58
Weighted Average Remaining Contractual Term (in years)
Nonvested as of March 31, 2018	1 year 3 months 7 days
Aggregate Intrinsic Value
Nonvested as of March 31, 2018 | $	$ 98,468

Stockholders' Equity - Stock-59

Stockholders' Equity - Stock-based Compensation Employee Stock Purchase Plan (Details) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected term (in years)	1 year 3 months 18 days	1 year 2 months 12 days
Expected volatility	35.70%	26.10%
Risk-free interest rate	1.90%	0.90%
Expected dividends	0.00%	0.00%
Weighted average fair value at grant date (USD per Share)	$ 78.38	$ 26.09

Common Stock Repurchase - Addit

Common Stock Repurchase - Additional Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	1 Months Ended
	Feb. 28, 2018	Nov. 30, 2017	May 31, 2017	Jan. 31, 2017	Mar. 31, 2018	Apr. 28, 2016
April 2014 Stock Repurchase Program
Share Repurchases [Line Items]
Accelerated share repurchase (shares)				40
Price ($ per share)				$ 96.37
Repurchased				$ 3.8
April 2016 Repurchase Program
Share Repurchases [Line Items]
Accelerated share repurchase (shares)	400
Price ($ per share)	$ 252.24
Repurchased	$ 100
Repurchase of common stock, common stock authorized						$ 300
Amount remaining in repurchase plan					$ 100
2017 ASR
Share Repurchases [Line Items]
Accelerated share repurchase (shares)		200	400
Price ($ per share)		$ 243.40	$ 146.48
Repurchased		$ 50	$ 50

Accounting for Income Taxes - A

Accounting for Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2017
Income Taxes [Line Items]
Provision for (benefit from) income taxes	$ 2,902		$ (7,223)
Effective income tax rate, continuing operations	2.90%		(11.40%)
Statutory federal income tax rate	35.00%
Unrecognized tax benefits	$ 50,300	$ 47,700		$ 47,700
Accrued penalties and interest	3,300
Unrecognized tax benefits that would impact effective tax rate	28,000
Undistributed earnings of foreign subsidiaries		606,500		606,500
Amount of no longer indefinitely reinvested foreign earnings				591,900
Deferred tax liability due in event of foreign earnings being distributed		3,300
Amount of indefinitely reinvested foreign earnings		14,700		$ 14,700
Additional income tax expense due to TCJA	$ 2,400	$ 84,300
Foreign Tax Authority
Income Taxes [Line Items]
Foreign income tax rate	30.00%		30.00%
Accounting Standards Update 2016-09
Income Taxes [Line Items]
Tax benefit	$ 23,300		$ 21,300

Computation of Basic and Dilute

Computation of Basic and Diluted Net Income Per Share Attributable to Common Stock (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 95,866	$ 69,420
Weighted-average common shares outstanding, basic	80,036	79,904
Dilutive effect of potential common stock	1,592	1,630
Total shares, diluted	81,628	81,534
Net income per share, basic	$ 1.20	$ 0.87
Net income per share, diluted	$ 1.17	$ 0.85

Segments and Geographical Inf63

Segments and Geographical Information - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018segment
Disclosure Segments And Geographical Information Additional Information [Abstract]
Number of reportable segments	2

Segments and Geographical Inf64

Segments and Geographical Information - Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Net revenues	$ 436,924	$ 310,341
Gross profit	327,408	235,625
Income from operations	98,192	61,673
Interest income	2,176	1,195
Depreciation and amortization	11,434	7,867
Other income (expense), net	177	450
Net income before provision for (benefit from) income taxes and equity in losses of investee	100,545	63,318
Operating segments
Segment Reporting Information [Line Items]
Income from operations	177,536	120,738
Clear Aligner
Segment Reporting Information [Line Items]
Net revenues	385,505	282,399
Gross profit	296,976	219,947
Income from operations	161,454	114,734
Depreciation and amortization	6,384	4,363
Scanner
Segment Reporting Information [Line Items]
Net revenues	51,419	27,942
Gross profit	30,432	15,678
Income from operations	16,082	6,004
Depreciation and amortization	1,104	1,037
Unallocated corporate expenses
Segment Reporting Information [Line Items]
Income from operations	(79,344)	(59,065)
Depreciation and amortization	$ 3,946	$ 2,467

Segments and Geographical Inf65

Segments and Geographical Information - Net Revenues by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Net revenues	$ 436,924	$ 310,341
United States
Segment Reporting Information [Line Items]
Net revenues	237,103	183,273
The Netherlands
Segment Reporting Information [Line Items]
Net revenues	139,531	99,799
Other International
Segment Reporting Information [Line Items]
Net revenues	$ 60,290	$ 27,269

Segments and Geographical Inf66

Segments and Geographical Information - Long-Lived Assets by Geographic Area (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Long-lived assets	$ 400,528	$ 348,793
The Netherlands
Segment Reporting Information [Line Items]
Long-lived assets	164,165	143,673
United States
Segment Reporting Information [Line Items]
Long-lived assets	126,983	128,171
Costa Rica
Segment Reporting Information [Line Items]
Long-lived assets	48,470	30,738
Mexico
Segment Reporting Information [Line Items]
Long-lived assets	30,215	25,090
China
Segment Reporting Information [Line Items]
Long-lived assets	12,258	5,480
Other International
Segment Reporting Information [Line Items]
Long-lived assets	$ 18,437	$ 15,641