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Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan (Stock Options Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Outstanding Stock Options Activity [Roll Forward] |  |  |
Outstanding at January 1 (in shares) | 694,881 |  |
Exercised (in shares) | (329,502) |  |
Canceled (in shares) | (8,993) |  |
Outstanding at December 31 (in shares) | 356,386 | 694,881 |
Vested and Expected to Vest at December 31(in shares) | 356,386 |  |
Exercisable at December 31 (in shares) | 340,503 |  |
Options Outstanding, Weighted Average Exercise Price [Roll Forward] |  |  |
Outstanding - weighted average exercise price per share | $ 11.33 |  |
Exercised, weighted average exercise price per share | 10.54 |  |
Canceled, weighted average exercise price per share | 9.81 |  |
Vested and Expected to Vest, weighted average exercise price per share | 12.11 |  |
Exercisable, weighted average exercise price per share | $ 11.94 |  |
Outstanding, weighted average remaining contractual term | 3 years 6 months | 3 years 6 months |
Vested and Expected to Vest, weighted average remaining contractual term | 3 years 6 months |  |
Exercisable, weighted average remaining contractual term | 3 years 3 months 18 days |  |
Options outstanding - aggregate intrinsic value | $ 11,705 | $ 15,189 |
Vested and Expected to Vest, aggregate intrinsic value | 11,705 |  |
Exercisable, aggregate intrinsic value | 11,241 |  |
Employee Stock Option [Member] |  |  |
Options Outstanding, Weighted Average Exercise Price [Roll Forward] |  |  |
Total intrinsic value of options exercised | $ 10,900 | $ 3,900 | $ 7,600
Incentive Stock Options [Member] |  |  |
Outstanding Stock Options Activity [Roll Forward] |  |  |
Outstanding at January 1 (in shares) | 4,267 |  |
Exercised (in shares) | (4,267) |  |
Canceled (in shares) | 0 |  |
Outstanding at December 31 (in shares) | 0 | 4,267 |
Vested and Expected to Vest at December 31(in shares) | 0 |  |
Exercisable at December 31 (in shares) | 0 |  |
Non Qualified Stock Options [Member] |  |  |
Outstanding Stock Options Activity [Roll Forward] |  |  |
Outstanding at January 1 (in shares) | 690,614 |  |
Exercised (in shares) | (325,235) |  |
Canceled (in shares) | (8,993) |  |
Outstanding at December 31 (in shares) | 356,386 | 690,614 |
Vested and Expected to Vest at December 31(in shares) | 356,386 |  |
Exercisable at December 31 (in shares) | 340,503 |  |

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- 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=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable 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)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + 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 (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to 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)(iv)(3) -URI http://asc.fasb.org/extlink&oid=6415400&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=6415400&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=6415400&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=6415400&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=6415400&loc=d3e5070-113901 + Details
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- Definition As of the balance sheet date, the weighted-average exercise price (at which grantees can acquire the shares reserved for issuance) for exercisable stock options that are fully vested or expected to vest. + 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 (e)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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