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Stock-Based Compensation Plans (Narrative) (Details) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 USD ($) plan shares | Jun. 30, 2017 USD ($) | Jun. 30, 2018 USD ($) plan shares | Jun. 30, 2017 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Compensation expense for share-based payments | $ | $ 4,465,634 | $ 3,406,371 | $ 8,366,949 | $ 6,890,611
Compensation cost capitalized as part of inventory | $ |  |  | $ 299,227 | 225,613
Employee Stock Option Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of shares available for grant (in shares) | shares | 24,000,000 |  | 24,000,000 |
Unrecognized compensation cost | $ | $ 10,140,213 |  | $ 10,140,213 |
Employee Stock Option Plan [Member] | Minimum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Option vesting period |  |  | 1 year |
Option expiration period |  |  | 5 years |
Employee Stock Option Plan [Member] | Maximum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Option vesting period |  |  | 5 years |
Option expiration period |  |  | 10 years |
Non Employee Director Stock Option Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Option vesting period |  |  | 6 months |
Option expiration period |  |  | 10 years |
Unrecognized compensation cost | $ | $ 198,044 |  | $ 198,044 |
Number of shares authorized (in shares) | shares | 1,000,000 |  | 1,000,000 |
Options granted (in shares) | shares |  |  | 476,000 |
Employee Stock Purchase Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Shares approved (in shares) | shares | 2,000,000 |  | 2,000,000 |
ESPP discount rate |  |  | 85.00% |
ESPP discount rate recognized as compensation expnese |  |  | 15.00% |
Shares granted (in shares) | shares | 863,395 |  | 863,395 |
Restricted Stock Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of shares authorized (in shares) | shares | 9,000,000 |  | 9,000,000 |
Restricted period, maximum, in years |  |  | 10 years |
Unearned stock-based compensation | $ | $ 32,362,619 |  | $ 32,362,619 |
Amortization expense | $ | $ 2,189,938 | $ 1,285,847 | $ 3,832,998 | $ 2,226,658
Equity Incentive Plans |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of plans | plan | 4 |  | 4 |
Stock Options |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of plans | plan | 2 |  | 2 |

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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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