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Equity Compensation Plans (Tables) | 12 Months Ended
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Dec. 31, 2017
Equity Compensation Plans [Abstract] |
Activity Under Stock Based Compensation Plans | Activity under the plans during 2017 was as follows: ﻿
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﻿ |  |  |  |  |  |  |  |  | Weighted |  |  |
﻿ |  |  |  |  |  | Weighted |  |  | Average |  |  |
﻿ |  |  | Number of |  |  | Average |  |  | Remaining |  |  | Aggregate
﻿ |  |  | Shares |  |  | Exercise |  |  | Contractual |  |  | Intrinsic
﻿Time-Based Stock Options |  |  | Outstanding |  |  | Price |  |  | Term |  |  | Value
﻿Outstanding at January 1, 2017 |  |  | 2,454 |  | $ | 12.51 |  |  |  |  |  |
﻿Granted |  |  | 65 |  |  | 20.22 |  |  |  |  |  |
﻿Exercised |  |  | (458) |  |  | 9.61 |  |  |  |  |  |
﻿Cancelled |  |  | (35) |  |  | 19.08 |  |  |  |  |  |
﻿Outstanding at December 31, 2017 |  |  | 2,026 |  | $ | 13.30 |  |  | 5.62 |  | $ | 11,730
﻿Vested and expected to vest |  |  | 2,004 |  | $ | 13.23 |  |  | 5.58 |  | $ | 11,717
﻿Exercisable at December 31, 2017 |  |  | 1,766 |  | $ | 12.48 |  |  | 5.20 |  | $ | 11,471
﻿ |  |  |  |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  | Weighted |  |  |  |  |  |
﻿ |  |  | Number of |  |  | Average |  |  |  |  |  |
﻿ |  |  | Shares |  |  | Grant Date |  |  |  |  |  |
﻿Restricted Stock |  |  | Outstanding |  |  | Fair Value |  |  |  |  |  |
﻿Outstanding at January 1, 2017 |  |  | 1,416 |  | $ | 17.40 |  |  |  |  |  |
﻿Awarded |  |  | 771 |  |  | 19.38 |  |  |  |  |  |
﻿Released |  |  | (331) |  |  | 17.43 |  |  |  |  |  |
﻿Forfeited |  |  | (11) |  |  | 18.52 |  |  |  |  |  |
﻿Outstanding at December 31, 2017 |  |  | 1,845 |  | $ | 18.22 |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  | Weighted |  |  |
﻿ |  |  |  |  |  | Weighted |  |  | Average |  |  |
﻿ |  |  | Number of |  |  | Average |  |  | Remaining |  |  | Aggregate
﻿ |  |  | Shares |  |  | Exercise |  |  | Contractual |  |  | Intrinsic
﻿Performance Stock Options |  |  | Outstanding |  |  | Price |  |  | Term |  |  | Value
﻿Outstanding at January 1, 2017 |  |  | 450 |  | $ | 13.48 |  |  |  |  |  |
﻿Granted |  |  | — |  |  | — |  |  |  |  |  |
﻿Exercised |  |  | — |  |  | — |  |  |  |  |  |
﻿Cancelled |  |  | — |  |  | — |  |  |  |  |  |
﻿Outstanding at December 31, 2017 |  |  | 450 |  | $ | 13.48 |  |  | 5.45 |  | $ | 2,774
﻿Exercisable at December 31, 2017 |  |  | 250 |  | $ | 13.48 |  |  | 5.45 |  | $ | 1,541
﻿ ﻿ Activity under the plans during 2016 was as follows: ﻿ ﻿
﻿ |  |  |  |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  | Weighted |  |  |
﻿ |  |  |  |  |  | Weighted |  |  | Average |  |  |
﻿ |  |  | Number of |  |  | Average |  |  | Remaining |  |  | Aggregate
﻿ |  |  | Shares |  |  | Exercise |  |  | Contractual |  |  | Intrinsic
﻿Time-Based Stock Options |  |  | Outstanding |  |  | Price |  |  | Term |  |  | Value
﻿Outstanding at January 1, 2016 |  |  | 2,734 |  | $ | 11.75 |  |  |  |  |  |
﻿Granted |  |  | 215 |  |  | 16.74 |  |  |  |  |  |
﻿Exercised |  |  | (394) |  |  | 8.47 |  |  |  |  |  |
﻿Cancelled |  |  | (101) |  |  | 16.66 |  |  |  |  |  |
﻿Outstanding at December 31, 2016 |  |  | 2,454 |  | $ | 12.51 |  |  | 6.02 |  | $ | 18,295
﻿Vested and expected to vest |  |  | 2,420 |  | $ | 12.42 |  |  | 5.99 |  | $ | 18,228
﻿Exercisable at December 31, 2016 |  |  | 1,914 |  | $ | 11.01 |  |  | 5.40 |  | $ | 16,897
﻿ |  |  |  |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  | Weighted |  |  |  |  |  |
﻿ |  |  | Number of |  |  | Average |  |  |  |  |  |
﻿ |  |  | Shares |  |  | Grant Date |  |  |  |  |  |
﻿Restricted Stock |  |  | Outstanding |  |  | Fair Value |  |  |  |  |  |
﻿Outstanding at January 1, 2016 |  |  | 1,071 |  | $ | 17.30 |  |  |  |  |  |
﻿Awarded |  |  | 710 |  |  | 16.35 |  |  |  |  |  |
﻿Forfeited |  |  | (70) |  |  | 17.31 |  |  |  |  |  |
﻿Released |  |  | (295) |  |  | 14.49 |  |  |  |  |  |
﻿Outstanding at December 31, 2016 |  |  | 1,416 |  | $ | 17.40 |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  | Weighted |  |  |
﻿ |  |  |  |  |  | Weighted |  |  | Average |  |  |
﻿ |  |  | Number of |  |  | Average |  |  | Remaining |  |  | Aggregate
﻿ |  |  | Shares |  |  | Exercise |  |  | Contractual |  |  | Intrinsic
﻿Performance Stock Options |  |  | Outstanding |  |  | Price |  |  | Term |  |  | Value
﻿Outstanding at January 1, 2016 |  |  | 450 |  | $ | 13.48 |  |  |  |  |  |
﻿Granted |  |  | — |  |  | — |  |  |  |  |  |
﻿Exercised |  |  | — |  |  | — |  |  |  |  |  |
﻿Cancelled |  |  | — |  |  | — |  |  |  |  |  |
﻿Outstanding at December 31, 2016 |  |  | 450 |  | $ | 13.48 |  |  | 6.45 |  | $ | 3,074
﻿Exercisable at December 31, 2016 |  |  | 250 |  | $ | 13.48 |  |  | 6.45 |  | $ | 1,708
﻿
Share-Based Compensation Expense Related to Employee Share-Based Compensation |
﻿ |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  |
﻿ |  | 2017 |  | 2016 |  | 2015
﻿Cost of revenue |  | $ | 610 |  | $ | 420 |  | $ | 416
﻿Research and development expenses |  |  | 2,052 |  |  | 1,825 |  |  | 1,373
﻿Selling, general and administrative expenses |  |  | 11,953 |  |  | 9,452 |  |  | 7,208
﻿Total |  | $ | 14,615 |  | $ | 11,697 |  | $ | 8,997
﻿
Assumptions Used for Determining Fair Value of Options |
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﻿ |  |  |  |  |  |  |  |  |  |  |  |
﻿ |  |  | 2017 |  |  | 2016 |  |  | 2015
﻿Risk-free interest rate |  |  | 1.75 - 2.12 | % |  |  | 1.06 - 2.02 | % |  |  | 1.30 - 1.96 | %
﻿Expected life of option (years) |  |  | 5.21 to 5.76 |  |  |  | 5.27 to 7.10 |  |  |  | 5.20 to 6.89 |
﻿Expected volatility of stock |  |  | 43.00 - 48.00 | % |  |  | 46.00 - 51.00 | % |  |  | 46.00 - 67.00 | %
﻿Weighted-average volatility |  |  | 44.50 | % |  |  | 48.87 | % |  |  | 54.75 | %
﻿Dividend yield |  |  | 0.00 | % |  |  | 0.00 | % |  |  | 0.00 | %
﻿
Weighted Average Estimated Grant Date Fair Value Per Share of Stock Options and Restricted Stock Granted |
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﻿ |  |  |  |  |  |  |  |  |  |  |
﻿ |  | 2017 |  |  | 2016 |  |  | 2015
﻿Stock options |  | $ | 8.60 |  |  | $ | 8.25 |  |  | $ | 11.12
﻿Restricted stock |  |  | 19.38 |  |  |  | 16.35 |  |  |  | 17.82
﻿
Estimated Grant Date Fair Value Per Share of Performance Options Granted |
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﻿ |  |  |  |  |  |  |  |  |  |  |
﻿ |  | Price |  |  | Fair Value of |  |  | Fair Value of
﻿ |  | Target |  |  | 2012 Grant |  |  | 2014 Grant
﻿Tranche 1 |  | $ | 10.00 |  |  | $ | 4.32 |  |  | $ | 14.74
﻿Tranche 2 |  |  | 12.50 |  |  |  | 4.30 |  |  |  | 14.74
﻿Tranche 3 |  |  | 15.00 |  |  |  | 4.27 |  |  |  | 14.74
﻿Tranche 4 |  |  | 17.50 |  |  |  | 4.23 |  |  |  | 14.74
﻿Tranche 5 |  |  | 20.00 |  |  |  | 4.19 |  |  |  | 14.73
﻿Tranche 6 |  |  | 25.00 |  |  |  | 4.10 |  |  |  | 14.73
﻿Tranche 7 |  |  | 30.00 |  |  |  | 4.01 |  |  |  | 14.71
﻿Tranche 8 |  |  | 35.00 |  |  |  | 3.92 |  |  |  | 14.67
﻿Tranche 9 |  |  | 40.00 |  |  |  | 3.83 |  |  |  | 14.61
﻿

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- Definition Tabular disclosure of the allocation of equity-based compensation costs to a given line item on the balance sheet and income statement for the period. This may include the reporting line for the costs and the amount capitalized and expensed. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 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 S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 + Details
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- Definition Tabular disclosure for share-based compensation plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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