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Note 15 - Stock-based Compensation - Summary of Information About Stock-based Awards Outstanding (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
Number of shares outstanding (in shares) | 1,548 | 2,565
Weighted average remaining contractual life in years, options outstanding (Year) | 4 years 73 days | 4 years 36 days
Aggregate intrinsic value, options outstanding | $ 34,990 | $ 51,959
Number of shares exercisable (in shares) | 432 | 557
Weighted average remaining contractual life in years, options exercisable (Year) | 3 years | 2 years 255 days
Aggregate intrinsic value, options exercisable | $ 13,523 | $ 15,827
Exercise Price 1 [Member] |  |
Exercise price (in dollars per share) |  | $ 18.56
Number of shares outstanding (in shares) | 23 | 15
Weighted average remaining contractual life in years, options outstanding (Year) | 3 years 328 days | 2 years 292 days
Aggregate intrinsic value, options outstanding | $ 1,455 | $ 526
Number of shares exercisable (in shares) |  | 15
Weighted average remaining contractual life in years, options exercisable (Year) |  | 2 years 292 days
Aggregate intrinsic value, options exercisable |  | $ 526
Exercise Price 2 [Member] |  |
Exercise price (in dollars per share) | $ 20.13 | $ 19.69
Number of shares outstanding (in shares) | 35 | 15
Weighted average remaining contractual life in years, options outstanding (Year) | 1 year 109 days | 2 years 219 days
Aggregate intrinsic value, options outstanding | $ 1,533 | $ 509
Number of shares exercisable (in shares) | 35 | 15
Weighted average remaining contractual life in years, options exercisable (Year) | 1 year 109 days | 2 years 219 days
Aggregate intrinsic value, options exercisable | $ 1,533 | $ 509
Exercise Price 3 [Member] |  |
Exercise price (in dollars per share) | $ 23.34 | $ 20.13
Number of shares outstanding (in shares) | 176 | 108
Weighted average remaining contractual life in years, options outstanding (Year) | 1 year 146 days | 2 years 109 days
Aggregate intrinsic value, options outstanding | $ 7,150 | $ 3,608
Number of shares exercisable (in shares) | 176 | 108
Weighted average remaining contractual life in years, options exercisable (Year) | 1 year 146 days | 2 years 109 days
Aggregate intrinsic value, options exercisable | $ 7,150 | $ 3,608
Exercise Price 4 [Member] |  |
Exercise price (in dollars per share) | $ 25.65 | $ 20.54
Number of shares outstanding (in shares) | 10 | 53
Weighted average remaining contractual life in years, options outstanding (Year) | 109 days | 2 years 109 days
Aggregate intrinsic value, options outstanding | $ 398 | $ 1,761
Number of shares exercisable (in shares) | 10 | 28
Weighted average remaining contractual life in years, options exercisable (Year) | 109 days | 2 years 109 days
Aggregate intrinsic value, options exercisable | $ 398 | $ 934
Exercise Price 5 [Member] |  |
Exercise price (in dollars per share) | $ 35.15 | $ 23.34
Number of shares outstanding (in shares) | 15 | 635
Weighted average remaining contractual life in years, options outstanding (Year) | 5 years 36 days | 2 years 146 days
Aggregate intrinsic value, options outstanding | $ 432 | $ 19,226
Number of shares exercisable (in shares) | 15 | 140
Weighted average remaining contractual life in years, options exercisable (Year) | 5 years 36 days | 2 years 146 days
Aggregate intrinsic value, options exercisable | $ 432 | $ 4,247
Exercise Price 6 [Member] |  |
Exercise price (in dollars per share) | $ 38.24 | $ 24.57
Number of shares outstanding (in shares) | 15 | 9
Weighted average remaining contractual life in years, options outstanding (Year) | 4 years 292 days | 2 years 36 days
Aggregate intrinsic value, options outstanding | $ 386 | $ 269
Number of shares exercisable (in shares) | 15 | 1
Weighted average remaining contractual life in years, options exercisable (Year) | 4 years 292 days | 2 years 36 days
Aggregate intrinsic value, options exercisable | $ 386 | $ 33
Exercise Price 7 [Member] |  |
Exercise price (in dollars per share) | $ 42.87 | $ 25.65
Number of shares outstanding (in shares) | 1,074 | 68
Weighted average remaining contractual life in years, options outstanding (Year) | 4 years 182 days | 1 year 109 days
Aggregate intrinsic value, options outstanding | $ 22,651 | $ 1,905
Number of shares exercisable (in shares) | 143 | 68
Weighted average remaining contractual life in years, options exercisable (Year) | 4 years 182 days | 1 year 109 days
Aggregate intrinsic value, options exercisable | $ 3,005 | $ 1,905
Exercise Price 8 [Member] |  |
Exercise price (in dollars per share) | $ 47.46 | $ 26.70
Number of shares outstanding (in shares) | 38 | 15
Weighted average remaining contractual life in years, options outstanding (Year) | 5 years 328 days | 3 years 292 days
Aggregate intrinsic value, options outstanding | $ 619 | $ 404
Number of shares exercisable (in shares) | 38 | 15
Weighted average remaining contractual life in years, options exercisable (Year) | 5 years 328 days | 3 years 292 days
Aggregate intrinsic value, options exercisable | $ 619 | $ 404
Exercise Price 9 [Member] |  |
Exercise price (in dollars per share) | $ 57.97 | $ 28.23
Number of shares outstanding (in shares) | 30 | 30
Weighted average remaining contractual life in years, options outstanding (Year) | 6 years 219 days | 4 years 292 days
Aggregate intrinsic value, options outstanding | $ 180 | $ 762
Number of shares exercisable (in shares) |  | 30
Weighted average remaining contractual life in years, options exercisable (Year) |  | 4 years 292 days
Aggregate intrinsic value, options exercisable |  | $ 762
Exercise Price 10 [Member] |  |
Exercise price (in dollars per share) | $ 58.79 | $ 29.52
Number of shares outstanding (in shares) | 23 | 400
Weighted average remaining contractual life in years, options outstanding (Year) | 4 years 182 days | 3 years 219 days
Aggregate intrinsic value, options outstanding | $ 120 | $ 9,640
Number of shares exercisable (in shares) |  | 75
Weighted average remaining contractual life in years, options exercisable (Year) |  | 3 years 219 days
Aggregate intrinsic value, options exercisable |  | $ 1,807
Exercise Price 11 [Member] |  |
Exercise price (in dollars per share) | $ 63.35 | $ 29.95
Number of shares outstanding (in shares) | 109 | 17
Weighted average remaining contractual life in years, options outstanding (Year) | 5 years 328 days | 109 days
Aggregate intrinsic value, options outstanding | $ 66 | $ 400
Number of shares exercisable (in shares) |  | 17
Weighted average remaining contractual life in years, options exercisable (Year) |  | 109 days
Aggregate intrinsic value, options exercisable |  | $ 400
Exercise Price 12 [Member] |  |
Exercise price (in dollars per share) |  | $ 35.15
Number of shares outstanding (in shares) |  | 15
Weighted average remaining contractual life in years, options outstanding (Year) |  | 6 years 36 days
Aggregate intrinsic value, options outstanding |  | $ 277
Number of shares exercisable (in shares) |  |
Weighted average remaining contractual life in years, options exercisable (Year) |  |
Aggregate intrinsic value, options exercisable |  |
Exercise Price 13 [Member] |  |
Exercise price (in dollars per share) |  | $ 38.24
Number of shares outstanding (in shares) |  | 45
Weighted average remaining contractual life in years, options outstanding (Year) |  | 5 years 292 days
Aggregate intrinsic value, options outstanding |  | $ 692
Number of shares exercisable (in shares) |  | 45
Weighted average remaining contractual life in years, options exercisable (Year) |  | 5 years 292 days
Aggregate intrinsic value, options exercisable |  | $ 692
Exercise Price 14 [Member] |  |
Exercise price (in dollars per share) |  | $ 42.87
Number of shares outstanding (in shares) |  | 1,080
Weighted average remaining contractual life in years, options outstanding (Year) |  | 5 years 182 days
Aggregate intrinsic value, options outstanding |  | $ 11,610
Number of shares exercisable (in shares) |  |
Weighted average remaining contractual life in years, options exercisable (Year) |  |
Aggregate intrinsic value, options exercisable |  |
Exercise Price 15 [Member] |  |
Exercise price (in dollars per share) |  | $ 47.46
Number of shares outstanding (in shares) |  | 60
Weighted average remaining contractual life in years, options outstanding (Year) |  | 6 years 328 days
Aggregate intrinsic value, options outstanding |  | $ 370
Number of shares exercisable (in shares) |  |
Weighted average remaining contractual life in years, options exercisable (Year) |  |
Aggregate intrinsic value, options exercisable |  |

X
- Definition The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan. + 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)(1)(iii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 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 (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. + 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)(1)(i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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