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Equity Compensation Plans - Options (Details) - USD ($) |  |  | 12 Months Ended |
--- | --- | --- | --- | ---
Dec. 31, 2017 | Dec. 31, 2009 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | May 31, 2016
Equity Compensation Plans |  |  |  |  |  |
Term of stock options granted | 10 years |  |  |  |  |
Vesting period | 3 years |  |  |  |  |
Exercised (in shares) |  |  |  | 1,500 |  |
2009 Plan |  |  |  |  |  |
Equity Compensation Plans |  |  |  |  |  |
Granted (in shares) |  | 16,500 |  |  |  |
Shares |  |  |  |  |  |
Ending outstanding (in shares) | 9,000 |  | 9,000 |  |  |
Stock options |  |  |  |  |  |
Equity Compensation Plans |  |  |  |  |  |
Total unrecognized compensation cost | $ 0 |  | $ 0 |  |  |
Shares |  |  |  |  |  |
Beginning outstanding (in shares) |  |  | 94,500 |  |  |
Canceled (in shares) |  |  | (44,500) |  |  |
Expired (in shares) |  |  | (41,000) |  |  |
Ending outstanding (in shares) | 9,000 |  | 9,000 | 94,500 |  |
Exercised (in dollars) |  |  |  | $ 2,790,000 |  |
Ending outstanding (in dollars) | $ 55,440,000 |  | $ 55,440,000 |  |  |
Exercisable at the end of the period (in dollars) | $ 55,440,000 |  | $ 55,440,000 |  |  |
Exercisable at end of period (in shares) | 9,000 |  | 9,000 |  |  |
Weighted Average Exercise Price |  |  |  |  |  |
Beginning outstanding (in dollars per share) |  |  | $ 25.82 |  |  |
Canceled (in dollars per share) |  |  | 27.75 |  |  |
Expired (in dollars per share) |  |  | 27.75 |  |  |
Ending outstanding (in dollars per share) | $ 7.49 |  | 7.49 | $ 25.82 |  |
Exercisable at end of period (in dollars per share) | $ 7.49 |  | $ 7.49 |  |  |
Weighted Average Remaining Contractual Term (years) |  |  |  |  |  |
Ending outstanding (in years) |  |  | 1 year 1 month 6 days |  |  |
Exercisable at end of period |  |  | 1 year 1 month 6 days |  |  |
Stock options | 2014 Plan |  |  |  |  |  |
Equity Compensation Plans |  |  |  |  |  |
Number of shares authorized |  |  |  |  | 375,000 | 975,000
Stock options | 2009 Plan |  |  |  |  |  |
Equity Compensation Plans |  |  |  |  |  |
Exercised (in shares) |  |  | 0 |  | 0 |

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- Definition Unrecognized cost of unvested options awarded to employees as compensation. + 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 (i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, 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 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements. + 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)(4) -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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